Not sure whether removing one disc, one caliper and one hose is going to make any real world difference in the weight (in any way that you'd notice when riding) as the biggest chunk of unsprung mass on the XTZ is chuffing great hub (and the heavy rim) - which you'd still be stuck with.

I'd also be a tad wary (in the UK anyway) about invalidating insurance - It'll look a bit suspect (and obvious) to insurance assessors (and PC Plod for that matter) that half of your front brake is missing! Not so bad if you do a fork conversion with a single disk, because it looks like it's meant to be that way. I'm not quite sure how you'd fair in the MOT either - with bit of your braking system obviously AWOL?

Just playing devil's advocate!

I do see where you're coming from.

BTW - Nice work on the "Tube Tube"!

__________________