Ring size around 1 and 11/16ths?

I’m still trying to nail down the perfect fit… and it seems like I’m stuck solidly between a ring size of 1 3/4 and 1 5/8. Any thoughts on these options:

1. Ordering custom sizes from Mature Metal? They use the same increments as cbk devices, whereas steelworx offers a 42mm size that might be closer to my ideal.
2. Modifying existing cbk rings for better sizing? I’m looking for a way to build up the 1 3/4 ring slightly to remove some slack. The best solution I’ve found so far is silicon sealer, but since it isn’t strictly medical grade, I’m not entirely convinced.

It’s not a dealbreaker, though it does impact security… With the 1 3/4 ring, there’s enough looseness—even with the smallest spacer—that the device can slide down quite a bit. If I’m soft, it might slip off completely… and when I’m hard, I suspect I could likely free myself.