Oho, sometimes I used CSG to deal with smooth lines. But you're right, it is buggy . It sometimes can get on my nerves,though. I can tell that it's gonna take you a lotta time to make a perfect smooth bodywork with only using a polygon tool and some help with knife tool
By the way, I do love some Russian cars due to its names and beautiful classic looks. Oh,I do agree with pnvv because you've totally improved the bodywork design :3
Well, I can help you out with the thruster thing. Thyme scripting may help you to make spring engines stronger when on throttle without the use of thrusters,I'll make a tutorial soon( once the collab between me and pnvv is finished ). Overall, Good Job