I would recommend deciding on a suitable front tire and buying a similar sized junk tire and building a mock up to confirm rider/body relationships. As good as 3d design programs are (even with bipeds) they can not always convey needed viewing angles for the rider/pilot and the ability to realistically fit in the model.
Good luck
Sage advice.
From where I sit I can offer this opinion.( notice I said
sit and clearly stated
opinion)
Suited up and strapped into a closed vehicle is a pretty poor approximation of comfortable. when it is hot, worse still humid, it goes from poor to abysmal. When you are forced to wait, it does happen, delay on the track or you just plain got ready too early it can affect your ability to act rationally, or even quickly. These are key ingredients when travelling on a slick surface at high speed with the very real chance you may need to operate safety gear.
Lying on your chest is not a comfortable way to wait. When I say
lying , I mean strapped down in an insulated suit with a helmet on.
There are other issues. I don't have the proper terminology but it is more difficult to balance in this position as well , the easiest position is sitting up ....as your ears get closer to your centre of gravity it gets less easy to determine......
My final point is the march of time. I weighed 158lb's from the age of sixteen to forty, Jack Dolan suggested it might be smart to design the car for someone bigger, alas.
I shot from 158 to 188+ in less time than it takes to say "Upsize !" At nearly 46 I'm still
just under 190 .....it makes everything a little harder to do and a little less comfortable in the confines of a cabin designed for someone a few sizes smaller..
When you're sitting on the line you want to be focused, clear headed and have all your faculties at your disposal.