Got it figured out for the most part in case anyone cares. Turns out the loose cassette cog problem was the outside seal I cut down that was keeping the cassette locknut for getting tightened all the way. There's no room for ANY outside seal in the freehub when you do this swap, so I'll have to get something at the hardware store as mention above to put over the end of the cassette to try to keep any dirt out.

Also I had reused the thin inner seal that was part of the UG freehub to seal it to the wheel hub body, and that's what was causing it to seem like it was binding up as I mentioned above, so I just did away with this and the freehub spins freely. Maybe if I greased it I would have been able to keep it on, but oh well. Knock on wood all seem fine now.

Thanks again for all the input