How about this: 5/off 4/off? White's got no timing problems, and will have an opportunity to hit at some point. If you make white hit on the four point, at least you might have a chance to hit back with an extra on five or six. If you get nothing else out of it, at least you have two more off. Even if you do get into trouble, having three on both the five and six points looks like it gives you more chances to be able to fill out your board later, if things get scrappy.

After considering 4/off, the play that XG suggests does not look that scary at all!

I think it's 9 blot numbers after 6/1 5/1 (don't forget 4-2) and 13 blot numbers after 5/off 5/1.

I might have played 6/1 5/1 over the board, but I can see 5/off 5/1 being better. This structure after 6/1 5/1 where you have 2 on the 6 and 3 on the 5 and then a dearth of spares on the lower points tends not to be particularly safe down the line, because you clear the 6 and then you're often left with a shotty structure.

Still, I'm pretty sure 6/1 5/1 is long-term safer than 5/off 5/1, which has its own mess of problems, but 5/off 5/1, when it gets hit, will have more checkers off and it wins more gammons when not hit. So that could make up for a bit of extra risk.

Sounds right, thank you! The gammons are certainly higher, 40 vs 36. The wins are the same. I think it is 9 shots vs 12 shots, but I might be missing something.
A: 65 64 63 62 53 66 55 = 12 shots
B: 64 54 42 66 55 44 - 9 shots

Yep 12 blotters. I was erroneously counting 44.

One point to consider here is that because of white's open 5 point (and buried checker), you will have a fair amount of life after you get hit, so hitting is nowhere near as bad as it would otherwise be. Also, the extra checker off wouldn't help you post-hit if his board were closed (he just doubles you out), whereas it does here.