Thank you, everyone who offered their observations on my project.  For the time being, I'm going with "gasket surface" - because it is the least expensive.  The first photo shows the two variants I've made.

Although I still like the elegance of using o-rings, the simplest way to put a suitable groove for the o-ring requires a $40 annular cutter that I don't know I'd ever have another use for.  I suppose that I could recover the cost of the tool, if enough other people wanted to buy such a part, but it also sounds like a lot of folks here are moving away from the bed mount.  So, I'm taking the KIS route.

Now I have another question.  It may be that I just haven't looked in the right places for the information I want, but I can't fathom what's going on with the pickup in the second photo.  The reason I made the part on the left of photo 1 was to provide clearance for the four disks that are staked into those recesses.  What are they there for?  There are four galleys leading from the inside of the center hole to the four recesses.  They look rather like freeze plugs, but the physics looks wrong for protecting against overpressure.  If I use the spacer on the right, do I induce some risk by blocking those disks?

ADVthanksANCE,
Dale_R
COZY MkIV #0497
Ch. 13 in-progress

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