We went from 275/70's to 305/70's with no troubles other than needing new wider wheels and some interference with the fender flares. 305's have about the same rating as the 295/80's but are not near as large in diameter.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '05 Odyssey