Vatree, There must have been something seriously wrong with the 200 to see that kind of gains with only 25hp.
As for the 300XS. There is virtually no difference in weight. In fact, they are both 505lbs. (20'' shaft).
Other than insurance, liability, and tournaments restrictions, I don't ANY reason why the boat itself would not be able to handle the engine.
I ran a 210 with a 250XS and am thinking of upgrading to a 300XS and just running 250 decals... LOL!!