Sorry for the slow replies- there are a lot of great ideas here.
Looking at the photos of the DRE towers, the offset angle is ~15 degrees...
We looked into it, and making an angled head is not too big a deal (the setup gets a little more complicated, but it's totally doable...)
Here are some shots of the models with a 15 degree tilt:
My only concern with them is that it eliminates one of the alignment possibilities- turning it 90 degrees from as shown makes the oarlock tilted 15 degrees back (or forward)... come to think of it, the only thing it would effect is the use of oar rights, which could be twisted in theory. maybe there's no downside?
As for sealed bearings- I found one that has about the right dims and properties, and is sealed on both ends. I don't have a price, but I can find one. Due to the size of the bearings, it would have to be an 'A' configuration, and we'd probably want them top and bottom. Ideally, for this situation, I'd turn the shafts of the oar locks to fit as well, completely eliminate slop, perfect slip fit, seal the whole thing with orings.
Those would be some seriously nice oar stands-
As a side note- I did some bases that will fit DRE tubing as well. Probably need to put that in the commercial forum.