David, did you need a shorter bottom bracket when you put the mtn crank on the Troll? OP, you can check your present chainline on the Troll by measuring from the center of the seat tube to the center of the middle chainring. If it is in the 45 mm range, you may need a shorter bottom bracket. If it is around 50 mm, you might be OK.

If you presently have a 5-arm crank, I'm not sure there are any 22 tooth chainrings that will fit it. Usually you have to go to a 4-arm mtn crank.