Any plane can snap if not set up properly, Shogun has told you how to set up properly. The Cap is "known" for it as in standard guise it comes with large elevators compared to other scale aerobats (extra, giles, etc)

As for your original question, putting in a 61 will make things worse not better. The extra thrust will be cancelled out by the extra weight of the engine, plus you will have to do something to get the CoG right as Shogun says.

The suggestion of a Saito 72 is good, but the new Saito 82 would be even better. It is basically the 72 but bored and stroked. I beleive that it can swing an apc 14x6 quite happily, which will give you lots of thrust (the 61 would struggle with a 14x6)