I would be overly concerned about the chain being WAY too tight if he managed to get the 45 tooth on.
Perhaps a quick, and cheap fix woulf be getting a 12t for the front.
Still not sure if that would provide enough slack in chain though.
_________________
2008 WR250X
Gearing: 13t - 48t
Power Commander 5 / PC-V
Airbox Door Removed - Flapper glued - AIS removed
FmF Q4
Bridgestone Battlax BT-003rs