Good idea, but this should have been released instead of the first game. Oh, and you still haven't changed the physics engine. A taller tower with a stronger base should be sturdier than a small one with a rubbish base.
for the 6k jump, max all stats and upgrades, then launch off the big ramp, go straight until about 100 mph, then use 1/3 of rockets, repeat until 6k reached....