many have done it..can say I'd recommend it myself.
harder on clutches and transmission, especially if you are a bigger guy, if you like to haul a wagon, or mud bog.
If you are thinking of this as a permanent arrangement then invest in a different sprocket set to compensate for the gearing change, then it will be fine.
Current toys..
1986 Honda 350X..trail bomb!
1985 Honda 250SX..my main mudder
1985 Honda 250ES..Back in Black Trike
Current non-trike toys:
1990 Honda TRX300FW
1995 Seadoo GTX
1998 Polaris Indy Lite 340(Nearly new looking)
1998 Polaris Touring 500
1998 Club Car (electric)