To all you 29er's out there!

I do have reservations however as I think the idea is to run two chainrings so that the axle position remains constant and the disc brake pads do not need to be adjusted. So my question; do you reckon swapping between the 17t and 19t cogs (with single chainring) would cause a large enough difference to warrant adjustment each time?

I'm a bit confused here. I can see why you'd be concerned about chainline ( although this would be fine if you used a multi speed chain ) What puzzles me is how the axle position is changed by switching between the 2 cogs on the freewheel & why the brakes would need adjusting? Surely moving the brake rotor out of alignment would involve moving the hub sideways, thus putting the whole wheel off centre :-/

What am I missing here?