the geometry is pretty specific to the bike so it's not such a good idea with just any ole frame. the idea with 29'ers in general is that bigger wheels means a bigger contact patch with the trail which means more traction. the larger circumference of the wheel means that it will roll over rocks and ruts without being impeded as easily as a 26" wheel. the larger volume tire means a plusher ride and a bike that is less dependant on suspension. the larger wheel also means more rotational mass which is nice once you get the bike up to speed (it takes less effort to keep it up to speed). the downside is that 29'ers handle a bit more sluggish on tight singletrack and they don't accelerate as quickly. so a 69'er is kind of a compromise between the two bikes. it accelerates well because of the smaller wheel up front, the handling isn't as slow, and you get the roll over anything momentum and traction of a bigger front wheel.