Aligning the SL-C is important to get the most out the car- or even to enjoy it. Even a superb handling car like the SL-C will handle like a pig if the alignment specs are wrong. If your car is darty, seems to take right-hand turns different than lefts, or generally seems not to handle like it should, it is almost certainly an alignment issue.
See the manual for a discussion about alignment and how to do it correctly.
You may find it easier to align the car, especially for racing purposes, with a set of scales and hub stands. This is what most race shops are doing nowadays, and the use of these tools makes precise alignments faster, easier, and more repeatable than most DIY tools like string and tape measures. Don't use the pushrods in the rear suspension to make adjustments to ride height. The pushrods need to be adjusted so that (1) they don't hit the upper control arm on full droop, and (2) so that they are the same length. Different length pushrods on each side of the car will cause the effective wheel rate to be different on each side on a bump, or in a curve, which will lead to a squirrely car. Set them to be the same length, and adjust the ride height with the spring collars on the coil overs. This is so because the rockers are rising rate, so if they are different at rest, side-to-side wheel rates will be different.
When a wheel moves through it's range on a car and the toe changes, it's called bumpsteer. You see it's effect mostly when hitting a bump, usually while you are turning: the car generally wants to turn into or out of the turn, seemingly without any steering input. Some drivers describe the car as nervous or squirrely.
In fact, the wheel actually is turning, but instead of the steering wheel being in control, the wheel turns in or out (i.e., changes toe) because of an improperly designed or adjusted suspension.
All cars have some bumpsteer; the key to handling is generally to minimize it, or for cars that already have good bumpsteer characteristics, to move the curve where you want it (More on that later).
The SL-C actually has a pretty good bumpsteer curve, but you adjust your car to get there. You need to fabricate spacers for each wheel that minimize the toe change as the wheel goes through it's range of motion. To adjust bumpsteer on the SL-C, you put spacers under the tie rod to raise or lower the tie rod until the change in toe is minimized as the wheel goes through it's range. You will typically need to use a longer bolt to attach the tie rod to the upright when you add spacers of the length needed to correct bumpsteer.
Most builders take their car to a competent race shop for a complete alignment and setup, and correcting bumpsteer is a part of that process (or should be- check to be sure the shop knows you want your car checked and corrected). To check bumpsteer, the shop will typically take the wheel off the car, check the range of motion with the spring on the car, mark the range, then remove the spring to make checking easier. A gauge is placed on the wheel that makes it easy to check small changes in toe, and the hub is now moved through the range of motion (meaning from full droop to full compression), measuring the exact change in toe about every half inch. Write down the toe changes, and you can see how you could plot them (plotting change in toe over the range of motion of the hub). If the toe stays constant throughout the full range, you are done. But realistically, there will be changes, and you can plot them as a curve. This is called a bump steer curve.
So now that you know what you have, how to fix it?
In some cars you can move the steering rack up or down. In the SL-C, the rack stays where it is, and the tie rods are adjusted up or down.
The answer lies in making small adjustments to the height of the tie rod relative to the upright. In the case of the SL-C, it means adjusting the tie rod to be lower. Begin by adding a few washers, and plotting the curve again. You should see a measurable change (if not, you are doing it wrong). Add a few more washers and you should get closer (or farther apart, depending on where you are in the process). Eventually you will hit a sweet spot where adding or removing washers makes the curve worse. That's when you measure your washer stack and fabricate a bushing of that exact height to replace the washer stack.
Note that as you get close, you may want to use AN washers, as they are flatter, and thinner, giving you finer changes. In the author's car, each stack ended up being an inch or more. Your car will vary, but if you are too far from this general starting point, consider checking everything again to be sure you are measuring correctly.
Any experienced race shop will know that you set bumpsteer before you make final toe adjustments, as moving the tie rods up and down will by themselves change toe- so get the toe close before you start working on bumpsteer, and be prepared to re-adjust the toe after you've finished setting the bumpsteer.
After you've corrected the bumpsteer and done a final toe adjustment, re-check the bumpsteer to be sure you still have the desired curve, as moving the tie rods in and out can also have an indirect effect on bumpsteer.
You'll need to do this for all 4 wheels. It's not uncommon for both rear or front wheels to need slightly different length spacers due to tolerance stackup, so don't be lazy and do one side and make two spacers, thinking you can save time-- check both sides on each axle.
DIY Or Race Shop?
The best way to accurately check for bumpsteer is to use the right tools, like a dedicated bumpsteer gauge. Most builders don't have one, or don't want to invest in one that will be used so rarely, and don't have the alignment skills anyway. If you do want to try to do this yourself, invest in a gauge like this one or any of the others from the usual sources. You may find it useful, especially if you have a race car, or are a serial builder!
For the rest of us, take the car to a competent race shop. You'll be happy with the results, and the car will handle to its potential.
If you are doing the car on the absolute cheap, or are just stubborn and can't take advice, at least fabricate spacers that bring the tie rods more or less parallel to the lower control arms. That will be in the universe, anyway, and better than nothing. But don't expect the handling to be pin-point sharp like a correctly aligned car will be.