I test drove a 40' Newmar on the 26k chassis. It had a 266" wheelbase. Very stable going straight. Power was acceptable (unloaded weight was a tad over 22k) and ride was good but I didn't like the mount of body roll on sharp corners. Now after doing some research I think the Roadmaster anti-roll bar upgrades would have made it good enough, so it's back on my radar again.
Now, it does spend a lot of time at high RPMs in the hills, but Newmar does a good job with sound insulating so that didn't really bother me. The new 2016 chassis makes more torque lower down, so it spends less time screaming and owners report it actually climbs better even with less HP, probably due to the flatter torque curve and better gearing.