Just thought I'd chip in my two cents... I have a Potomac that I use on my HH Expedition side-zip. It fits perfectly with minimal fiddle-factor. I use the Triangle Thingies on my heavier down quilts that tend to sag more.
All my other UQ's are 2/3 or 3/4 length, but I've come to really appreciate the full length coverage of the Potomac. It's very luxurious!
The Potomac, specifically in use with a HH Exped zip, is a sweet rig and I give it two thumbs up.
Side note, I lent my Potomac to Wanderlust62 for use on his HH Safari during the Sylvania trip and he reported it worked great! I was wondering about the fit since the Safari is much larger than the Expedition, but he was evidently snug and warm.
"I know the feeling - It is the real thing - You can't refuse the embrace!" | "Go n-éirí an bóthar leat."