OK. Most of this was from Juz - can't claim any credit for it!
For an un-modified harness:
- Unclip and extend the straps of the right CL (it's the one on the left as you face the unit) - leave a few centimetres so you can tighten them easily.
- Lift this CL, with the mouthpiece, up and over the back of the box - it should stay there.
- Fit and extend both straps on the left CL, leaving a few centimetres as before
- Sit down with your back to the Inspo and slip your hand in through the left CL, making sure AutoAir etc is on the correct side of your arm.
- (At this point, I fit DS hose, bring waist strap across, fit crotch strap and tighten, fit waist strap and tighten - you'll probably have a different order)
- Tighten left CL straps
- Reach back and pull right CL down - the mouthpiece etc should come with it
- Fit and tighten right CL straps
Then I locate handsets etc etc
Doing this makes the process feel much less of a struggle.
Some of the guys have replaced the CL strap with a loop of bungee which they thread the waist strap through - this seems even easier.
HTH.