Originally Posted by
D-Fuzz
With regards to the staggered sizes from front to back, is it important for each tire to be of similar tread type or can they be different?
No, not important at all.
Tread isn't terribly important in gravel, there's no tread that's going to make you grip when the gravel is loose.
The smaller tire in back thing -- some people do that for mud clearance. I don't, because it usually doesn't rain that much where I live and I avoid riding in the mud if possible.