Chuck:
Your set-up resembles mine in most every way, though yours is a bit more industrial in scale. I got my plans from Mike Orlen.
I have bent many of my stocks and those of my friends, and so far, no problems, knock on wood. I would not want to work on a gun that has had any repairs in the wrist, however.
I've bent both through-bolt and conventional box locks and side-locks.
I use common mineral oil, which doesn't smell as it heats.
Like you, I mask off the areas of wood with foil that I don't want to heat. This concentrates the heat on the wrist.
I keep my lamps about 10-11 inches away from the wood. I wrap the wrist with a long cotton strip about 2" wide. Every 5-10 minutes, I brush on enough oil to saturate the wrap.
I have an aluminum drip pan underneath the wrist to keep my work area as clean as possible.
Unfortunately I find that the oil will migrate into the action, so I strip each gun after I bend it to remove this excess. I haven't found a way to prevent this and don't know of a material that would block the flow of oil and not be affected by the heat.
This process really works for me, and I like the ability to custom fit my stocks.
