I think I understand how Aerotech type motors are retained (a flange at the base of the motor that provides both retention and thrust ring functions). So after you build a rocket to take Aerotech SU or RMS (with no thrust ring and flange-holder of some sort), how do you use an Estes-type engine in that rocket? I've heard people say friction fit, but I prefer something a little more positive. I am really at a disadvantage here because there are no vendors locally for anything other than Estes engines, so I can't just look at it and figure it out. Sorry if this is an obvious question.