Having a lot of rudder command and practice flying knife edge is really good.
Another thing that helps spin proof a model is simply go with generous wing span. A 6 foot span model [built really light] will still be extremely sporty with a pair of 15s.
I used to fly 6 foot span RC Combat planes that weighed 40 ozs with a single LA .15 / 8x3 prop and it was a pretty good flyer lugging around that much weight plus the drag of streamers.
I'd run 7x5 props on your CVA 15s and just be quick to cut power if you run into any trouble. Make the first model effort a simple one to get your feet wet..then fly the heck out of it while you dream about other twins you'ld like to build.
I have a lightly built 5 foot span biplane with a pair of .049 TDs that is a pretty sporty flyer and I look forward to having one engine shut off before the other because then the model can be flown the rest of the time in knife edge and still maintain altitude.