If you want to sidemount a single unit just stick with o-t-s lungs.
As was done with the PRISM in the pic below (from SMI's website).

Tanks are MK spheres mounted underneath the unit I believe.
For two RBs I'd probably give a second pair of rearmounted lungs a shot.

The Shadow Pack CLs are the same as SMI's, but without the ADV and manual O2 add valve openings
and should work well.
Or a design like the Joker if you can manage to mount the CL next to our own lungs.
But back to the Sentinel, I find it curious that C2R reversed the gas path they used on the Ouroboros.
Wonder why they did that. Seems that other manufacturers that want(ed) to cater to the
military market all went with the counterclockwise flow.
Not that it did much good for them ...
Also, the choice of the 6 lbs cartridge has me a bit baffled. While the longer duration may well
be worth it, those cartridges will be even harder to come by on a trip.
The Optima's 5 lbs cartridge is just starting to become available at trip destinations, and that unit
has some good sales to show for.
The new displays look good though. Any word if they'll filter down to the Ouroboros, URM and VR3?