Hi Ted; didn't you read the contest rules? We are not suppose to tell anyone what we are building, so I cannot tell you that I am buliding a 4.3X Estes Falcon with a 4 1/2 foot wingspan. But then they also, (whoever the nefarious "THEY" might be) said that contest judges cannot enter the contest, so I guess I have two strikes against me now. (I was going to build a 6X 6" dia. Trident, but I decided against it because of needing 9 custom nose cones!) 😯

I'm looking at an Estes Ricochet. Questions as to how to fit a 75mm motor tube in it?

I'm in it for fun as much as anything. I get a kick out of seeing an Estes upscale in just about any format. It does give me the opportunity to build another rocket...

I guess it would be about a 4X upscale. Start with a 4" tube and upscale from there. Easy to do in RockSim. Then you can put a 75mm motor mount tube in it and do thru the wall fin attachment. Once you have a basic plan, it should be very easy to do. You might want to plan on dual deploy. But I guess all of this is a SOTO. (Statement Of The Obvious). It will be a cool rocket and fun to build and fly. As far as degree of difficulty in up-scaling, I am uncertain of this. I think the hardest part would be to build a scale nosecone.