I'm not familiar with the phoenix kit, but I did a very similar thing on a 40 size Great Planes super decathlon. I flew it with an os 40 through one crash, then rebuilt the plane and put an os 61 on it. It was scale...sort-of with the 40, but with the rebuild, I added extra epoxy, new firewall, doublers...a much heavier plane...counting the heavier engine. After the rebuild, I doubt that the little 40 would have done much but taxi it. With that 61, which was a powerhouse, it had awesome performance....not scale, but lots of vertical.

In fact, It had such an excess of power, that I was able to shoe-horn another tank, smoke pump, and muffler on it...rebalancing it of course. It flew great. Even with the extra power, you could slow it down ok, though with the extra weight, it landed faster. I took the wheel pants off because of it...didn't want them snagging our rough field and flipping it at such a fast landing speed.

My brother John said "Hey, can I fly it?"

Well, it went through a stand of trees...and before I could shake my head, it flew back out unscathed...but my already panicked brother dumb-thumbed it BACK into the trees, hitting every tree all the way down a creek bottom, landing in 4 feet of water. Radio trashed..engine survived.

As for your question... balance it right and be ready for a hotter airplane...that's all I know....except I know not to say yes to my brother.