The ends of the tubes are closed and the engines fit in loosely, so the chute charge will just blow the rocket engine out of the tube. I plan to use a small peice of masking tape to keep the engines in the tubes and the ignighters inserted in the engines until I light em, after they are lit they should burn through the masking tape and the thrust should hold them in the tubes.

It will not send any flame or heat into the car at all. I plan to test the tubes off of the vehicle first just to be sure, but I've built enough rockets to know what these ejection charges do, so I am about 99% sure there will be no issue, and I know there is absolutely no way it can ignite the tank or melt anything more that the rear skid. There is no way it will cook the rusty. The only way I might have issues is if one of the d engines fails catastrophically, but I wouldn't expect more than a blown engine tube and a scorched rear skid plate if that happens.

My biggest concern is that it may all be just a waste because 2 d engines may not produce enough thrust to make it worth all of the work, but if that turns out to be a problem, I will just take it out at night and get it on film, even if it doesn.t make it run much faster it will look awesome on film at night.