I have run both sizes, no day and night difference in keeping the tire on. now if your going way down as stated get some bead locks. the main part holding the tire is the psi, the force of the psi on the inner side wall is the same in either rim..10 psi is 10psi, thus the factor become if there is extra force being applied by the tire lip itself between the two rims sizes.. I am not sure on those loads, and have not seen any data. would love to see it to compare.