Will I fit in the car? This is a common question, and the answer may be surprising: You probably will, no matter your size, even if you are pretty tall, if you are willing to recline a bit.
There are fundamentally two areas that determine how well anyone fits in a car. The first is foot room. Luckily, the SL-C has really long footwells, so drivers (or passengers) with really long legs won't have a problem here. You won't have to move your legs sideways, or otherwise emulate a pretzel to fit.
In addition, the car can be ordered with an extended drivers footbox which allows the pedal assembly to be pushed even farther forward, allowing even NBA forwards to fit just fine. So legroom really isn't a problem at all, almost without regard to how long your legs are.
The second determinant to fitting in a car is headroom. This is where all cars of this type (except for open cars like the Superlite LeMans, which is an open-top version of the SL-C) begin to struggle. With a car that is even lower than a Lamborghini Aventador, it isn't surprising that headroom is at a premium.
The car is really quite low just 43" above the ground so it's obvious that there isn't an unlimited amount of headroom. So how do those NBA players fit? The answer is in careful selection and placement of seats, pedal location and steering wheel adjustment so that they are reclined enough to allow really tall drivers to fit. Also, the SL-C offers a couple of tricks. One is no-cost optional dropped floorpans, which allow the seat to be mounted lower than the rest of the floor. (You probably don't need the dropped floorpans if you never have a taller driver than about 5' 7". Anyone taller will benefit from the increased headroom the dropped floors provide.) Another is a selection of stock seats which are extremely low profile, adding more effective headroom. And third, is standard seat mount brackets that are drilled from the factory with multiple positions so you can mount the seat just the way you need to, to get the fit just right.
Seat selection and mounting is the most critical part of fitting tall people in the SL-C.
Really tall drivers will find that a reclined seating position can really increase apparent headroom, even allowing a helmet. For example, the author is 6' tall, and of normal proportion in terms of leg-to-torso ratio. With a seat bottom on the floor, and the seatback reclined at a 45 degree angle, there is about 2-3 inches of clearance- more than enough for a helmet. Drivers that are even taller will find that more seatback angle will yield much more headroom.
We've had people fit in the car who were almost 7' tall, so there is hope for almost everyone.
It's important to note that most aftermarket seats just don't work in the car. They are typically too wide at the top, too tall, and most of all, too high in the seat bottom. The factory seats, particularly the single-shell ones, are as thin as possible, and offer the lowest seating position possible, and the most flexibility, compared to seats of other design. The seats discussion elsewhere in the wiki has a good discussion of seats, and a spreadsheet showing sizes of many popular aftermarket seats.
Visiting to Check Fit
As mentioned above, proper fitment is more than just careful selection of parts. The same seats, pedals, etc in the same car can yield widely different results due to subtle variations in mounting. That makes a trip to "see if I fit" in another car often a wasted exercise. For example, the author's SL-C has a dropped floor, Tillett B5 seats, and the stock Tilton pedals. At just over 6 feet tall, he fits perfectly in his SL-C, with room for a helmet. But in trying to fit in another SL-C, with the same dropped floor, same pedals, and the same seats, he was very uncomfortable. What happened? The seats were mounted slightly differently, as were the pedals. The differences were very subtle, but each car was a good fit for the owner, just not for everyone else.
If you do make a trip to check fit in the car, and fit fine, that's great. But if you aren't comfortable, don't despair. Just remember that you can fit. You'll just have to be sure to be very specific about seat mounting, pedal location, and adjusting the steering wheel to get a perfect fit. Don't be concerned about whether or not you fit in any one car that's really irrelevant unless you are buying that specific car. Careful mounting and subtle adjustments make all the difference.
These aren't production cars with hard points and seats and adjustment ranges that are set at the factory. You can make the car fit you with just a little forethought and testing!