There is a difference between the Hope No2 and the Hope GT caliper. Most Lobo's I see are running a Hope No2, which uses the short axle plus the special bolt at the dropout. This leaves a metal on metal interface.
Probelm is Hope No2 is not designed to rotate, it is designed for a bike without rear disc mount and the caliper would remain fixed or close to. The torque arm, whatever you want to call it would normally sit on the upper stays, so the caliper won't move but on the Lobo the mount point is the lower stay, which means the caliper does move as the swingarm moves.
Hope GT caliper is designed to rotate (float) around the special bolt as the rear moves up and down, it has a plastic bushing in there along with a slightly different sized dropout bolt to the Hope No2.
You need any Big Un or Bulb, plus the short axle and the dropout bolt. I have an axle spare I *think* but I do not have the bolt.
I wouldn't fix the caliper, it's there to stop brake jack and is an integral part of the build imo.
See my bike, black one is stamped GT and the other was a spare I picked up, No2 I believe. GT Caliper is 155mm disc and the No2 I have is 165mm.
I will post pics of the bolt / axles when I get home
97 GT LTS
99 GT Lobo DH 1000 x 2