Welcome to HF, Brawny

Tried the Hennessy lashing. Hated it. Never tried the descender rings myself but it works well for many.

I used the supershelter & reflecting pad on my HH for years in similar temp ranges. By itself, the undercover is a great wind/rain/mosquito blocker and I left it on almost every night. Down to 45 or so the underpad & space blanket were all I ever needed (but I replaced the space blanket with a heavier/easier to handle version from SOL).

The bottom of your temp range is near my edge for the supershelter. Starting around 45, I add a little extra warmth by sleeping on top of a Wal- Mart fleece blanket. That and thermals worked well enough on the few nights it dipped below freezing.

I eventually switched to a 20 degree UQ and it's bulkier, but it's a whole bunch warmer, easier to adjust when you're laying in it, with a much bigger "covered area" .

Yup, any underquilt will fit a HH. It's just a rectangular quilt that's suspended up against you. If you want to use the bottom exit, just reach a foot through and push the UQ aside. Jacks R Better makes a UQ specifically for bottom entry HH, if that's you thing.