ChrisSpad

Please don't put people's names as the subject of posts, the whole point of a forum is for everyone to be able to share their knowledge.

So, i'll give you my opinion, and even what its based on. FrankC29 built one for his OS 25fx, there's a link to the video on his site of him flying it, it didn't have any problems hovering into a bit of wind, and i think it would hover and pull out with no wind at all, but, maybe he'll chime in here.
Now, i've only owned one fox engine, and it was a 40bb, and it was a heck of a stout engine. If their 25 is like their 40, i suspect it'd keep up with the 25fx no problem.
Something else to consider is your altitude, i live at near sea level, and i believe Frank does as well, if your altitude is higher, you'll need more engine, or a lighter plane. Landing gear weighs a bunch as well, it can be lost for alot of times 5 or 6 oz of weight savings. I think Kraut went from 1"x1/8" wide aluminum to 5/32" wire, and saved 4 oz. Thats a chunk of weight to remove from a 25 sized plane.
The key is going to be to keep it light. There's a huge difference in wheel weights as well. Some weigh as much as 2 oz each, and other foamies weigh 1/2 oz each. By using lighter wheels thats another 3 oz weight savings. The gear you use makes a big differnce as well. An ounce or two here or there really adds up quickly.
One more consideration is prop size. For thrust, depending on the engine, a 9x4 mas, 9x4 apc, or 10x3 apc will probably put out the most thrust. I'd suspect that the fox would really like the 10x3 apc, but thats pure speculation.
One of the most common mistakes i see is people putting high pitched props on these planes, and wondering why they won't hover well, or at all, and why they flutter at half throttle. Pitch=speed. Speed=flutter on these planes. Plain and simple.

Ok, rant off.