When the smallest shouldn't be, but is too big?

So alittle background. I've been self locking for a while now and I've had multiple devices. Currently I have the htv2. And it's very comfortable for long periods of wear.
But I'm running into a problem.

Generally my ring size is 39mm. I usually go 40 cause going down is too uncomfortable. And generally Every other device this has fit when I ordered the 40 it would sag waay from my body and not fully stop erections.

Nbd I went down to the 38 cause why not. But i still have the same problem (albeit to a lesser degree) but the ring still doesnt fit snugly. I've tried most things from taping it smaller to string thongs and while the string thongs work (ish). I get the kicked in the balls feeling really early on into the lockup.

I would go down if there was another size but there isn't.

You guys and gals have any thoughts or solutions?