Shawn, one thing to try:(posted 8735 days ago)There are lighter MF cameras than the Pentax, though not many 6x7 cameras. If you're kinda-sorta mostly comfortable with it, consider a monopod. If you're mostly an eye-level shooter--not changing view height frequently--that'll offload the weight off of your arms, and let you concentrate on your subject and the piddly bits of exposure and focus.
Years and years ago, I shot weddings with a mixed format set: one 35mm SLR and one MF TLR. The TLR used a waistlevel finder, and was either strapped snugly to my check, where I'd aim using 'body english', or lived on a monopod.
You'd think it'd be slower than no support, but I found it easier and therefore more convenient; give it a try. (It also works for 35mm...)