yes your going to have issue's, you will be needing full throttle a LOT more than Honda designed the motor to run,and even at full throttle, I think its going to struggle to even come close to spinning them in good mud, its a 30 something hp motor,? made to run on 25 inch tires, your asking it to spin a tire 20 % larger than designed for,
BUT then again think of this
your a guy that is planning to use there atv for a mud machine/water bug
the costs of doing so will shorten your life of your motor any way you look at it here, as your GOING to sink this motor sooner or later any how?
so LONG term life shouldn't be a concern for your motor period LOL
SO< as they it say, it costs money to play??
but yes 100% you NEED a GR, be silly NOT to add one!