you could definitely improve this by making the chassis longer and more compact, and not using any super tall gearing, you can make the gearing horizontal as well

The wings on top are upsidedown. you are going out of control because you are making the wings push you down instead of push you up. the only reason you are getting any height at all is because of the very few correctly placed wings pointing DOWN

You cant get more top speed because the gears and torque cant handle it and you dont have more gears to get to actual top speed My build i have has one 3 step shifter and one 2 step shifter And thus, it can now go like somehow 9 gears on my build, i have video of it on my youtube, you can acheive like 300mph with only 130+ hp with my transmission setup, stay on one side, do not make your gear transition to another plane like from horizintal to vertical as it only makes your builds lot bigger and cumbersome