Back-mounted Doubles with Hollis SMS100

I am wondering if there would be anything wrong with sandwiching a back-plate between the soft plate and the detachable "lumbar/back-guard(not sure what it's called)" on the SMS100 harness? My belief is that doing so would be a lot more stable than just using the "over-size washers" that are normally used for back-mounted doubles on a soft-plate harness. It would also be nice to take 6 pounds out of my weight pockets. I would of course not use the plate when side-mounting.