Bad news: I've done some calculations, and the 4 inches I'd like to add takes the trail geometry out a little farther than what is considered optimal. I've already bought a rear tire that is about one inch taller than stock. It will raise the rear axle by about 1/2 inch. But it would be best to raise the rear another 1-1/2" to get the trail back in line, and also I wouldn't mind having the ground clearance anyways.