Need some help here - - ->

[PKRWUD]

I am in a contest of sorts with a friend of mine. He claims that he can come up with 45 words, using ONLY the letters below. The rules are:

(1) Words must be a minimum of four letters.
(2) No letter may be used more than once, except for two "UÕs".
(3) Singular or plural of a word but not both.
(4) No proper names.

I tried, and couldn't even come close, so I figured before admitting defeat, I'd see what you guys (and gals) could come up with.

The letters are:

A G O P R S U U Y