I would not be surprised if there are different versions of DR TravelPac, but with the current version:
Referencing this side, it LOOKS like you could go
WING, Weight pouch rear loop, Shoulder T, Weight pouch front loop, Hip Belt loop
- or -
WING, Shoulder T, Weight pouch rear loop, Hip Belt loop, Weight pouch front loop - although this would put the weight pretty far forward and push the belt-mounted D forward too.
Maybe, you would have to measure ...
WING, Shoulder T, Weight pouch rear loop,Weight pouch front loop, Hip Belt loop
FWIW: Zeagle also makes add-on pockets that do not have clip-in weight carriers, but instead are loaded/unloaded via a top-zipper, but have solidly, velcro-secured bottom pull-dump handles.
There are 2, slightly different versions, both should have a single 2" wide loop to secure it to the belt and then either assembly screws for a compatible backplate or a velcro tab thing which could get somehow attached to something. Neither of the secondary stabilizers (assembly screws or tab) would likely work without some modification of either tab or DR backpad. That said, it is probably unnecessary if you trap them from sliding, either behind or ahead of the shoulder-strap Ts. I previously used them on my OMS IQ Pack with them just secured and located using the belt hardware, now they are on my son's LiteHawk since I went to OMS's similarly dumping combo utility/weight pockets. I prefer the carrierless pocket style personally, since there is less bulk, less empty-weight, and nothing to lose accidentally or in a deliberate weight dump (except the weights themselves) no trip-over or revert to weight belt issues because of a missing carrier ...
They are slightly narrower and taller than the OMS pouches about 5.5"W x 9"T
Zip-Touch:
Zip Touch Weight System
Rear-Weight:
Rear Weight System 20lb