[scuzz]

Um...I don't know about it being dangerous, but it would make the quad a little taller (by only an inch and a half mind you)

I think you can leave the heelgards on, but it might be tight. (no heel guards would be the most dangerous thing to me)

 

[scuzz]

Remember that from a 20 to a 22 inch tire only grants you 1 inch of clearance (or lack therof)

Like Chris said though, your results may vary according to how the manufacturer deems measuring them.