Kevin, one thing you could try is a UNF 10-32 screw. The listed diameter of a 10-32 is a hair bigger in diameter compared the original 3/16" Cycle and I have had success with these without resorting to tapping the captive nuts on the inner.
If your captive nuts are really flogged out then this is probably not going to help but would be worth a look I think.
The original 3/16" Cycle are listed as having a major diameter of 0.1875" (32TPI).
2BA are a whisker thinner at 0.1850" (31.4TPI).
10-32 UNF are a whisker larger at 0.1900" (32TPI).
Of course manufacturing tolerances will mean the 2BA & 10-32 screws available now will vary slightly from supplier to supplier but I have found the 10-32 screws to be a really nice fit and they are available with fillester heads as a bonus.
When I was building my primary case, I brazed new nuts on all round. The bottom half I then filled with extra braze around the holes and dressed back & /tapped through to increase the mating surface, no leaks so far, 300 miles into bedding her in.
