That looks rad! 
Thanks vod. I'm pretty proud of how it turned out.
The v1 harness worked but it was just so, so ugly and hard to actually put on. So I made a new one.
I started with an abbreviated variation of my flak vest pattern, done in natural linen. Each panel is two layers. I used cotton webbing for the shoulder straps, and doubled slides to secure the harness loop straps to make it adjustable but secure.

And added a front extension, in leftover flight suit material (so it blends if it peeks out) and leftover black linen from making the vest. It ended up looking a little bit PI with the topstitching and the overall shape of it.
After primary construction was done, I installed two snaps in each lower corner and matching snaps on the front belt loops on my pants.
The panel pulls the weight of the jetpack forward and down - I found that V1 would let my collar plate creep up and back a little too much for my liking.
The snaps keep everything flexible.


I initially went with simple D-ring style closures, but didn't like how the strap ends were loose (a major issue with the V1), so I added a bit of stitch-on velcro to both add security and neaten everything up.

It's really solid, secure, and much more attractive. I was able to wear my jetpack from about 12:30 to 4:00 comfortably at a local con.
It doesn't wobble at all.
I can jump up and down (done while demonstrating the attachment to some very nice potential Mandos), shimmy side to side, jog/run, bend over to pick things up etc without it shifting.
So, great success overall.