The frame looks nice but could be a lot stiffer. Why didn't you made a triangel in the middle of the frame (where the curved tube come together).
How are you going to mound your engine? With a bar to the back of your engine or underneath? Looks very nice so far.
Because the current construction is more than strong enough. How can you determen if it would be a lot stiffer? any more tubes would just be overkill and waste of performance - destroy the look / curves.
I don't say this design is not stiff enough and i am not talking about design. Only about to get the lightest frame, with the stiffest structure. I don't know how well you knowledge goes in calculation these kind of structures, but know all the tubes are seperated from each other. The have freedom to bend in all directions. By connection the tubes with a triangel, it would connected the tubes on there most flexible place. This make sure that the tubes don't have the freedom anymore that they did have. I hop you understand what I say :+.
Good luck with your frame.
Why such a heavy wheel @ the front?
He's right. There are much lighter wheels than this sonic disc rim. The SA drag wheel isn't that light either.. But looking to your project you don't take building a lightweight sprinter that serious. Looks good though.