Cat,
Good luck.  It seems that if you paper patch for anything other than a .45 you're the only person in the world trying that caliber.
You might benefit from .38-55 shooters.  That's very similar to .375 Win in case size/shape.  If you're considering 4227 I'm guessing you have velocity limitations?
Otherwise I thought RL-7 was the favorite for .375 Win shooters.  I don't have a .375 of either flavor, but I was very near buying one.  Let a '94 Big Bore slip by for $350!  But I got a .35 Whelen instead - try to find another paper-patcher for .35 Whelen.