My proposed Patriot setup
I would have to say it should work fine. I can see you might have a problem with the 75 for two reasons. First of all it has a wide crankcase and it might be a tricky fit. Second, the motor weighs about half again what a 40 weighs.
I built one a couple of years ago with an MDS 58 (which weighs a little bit more than a 46) on the nose and standard size servos and a 1100 mAh battery pack as far back as I could get it. It also had full retracts. It still needed about an ounce of weight on the tail. I'm guessing it will come out a little on the heavier side, me thinks?
I recenlty obtained a new kit. The motor will be a Jett Fire 60L with the pipe down the side. It will break the bank, but I love speed. I've already broken the bank once with a Jett 50 and it was well worth the bank breaking. I'm hoping for 140+ mph. The only probelm I have is my altitude and a loss in power.