I'm new to this forum, returning to MR after several years absence. I'm presently finishing a Comanche-3, looking to change the engine configuration. I've flown this model many times in the past... twice turning it into a 4-stage missile (using D12-0's for the intitial two stages...) I'm good at enhancing the body/fins for launch integrity. My question: can I use BP D12-0's for boosting 1&2, and then an E-12-4 for the top stage?