I've used gathered end underquilts on my RR. I did it for the first year or so I had one and it basically eliminates a few of my favorite RR features. With a RR you only need about 30 or so inches width of insulation, but regular underquilts can be up to twice that width. A RR underquilt, if properly sized, shouldn't wrap up over the sides like in a gathered end. If it does it voids your great view (which is amazing to have in a RR) as well as makes the saddle bag style pockets over the side useless as they will sag when full and pull the UQ away from your body underneath and create an air gap.
If you're handy with DIY or even if you aren't, I'd recommend shrinking your UQ down to 30ish inches wide and securing the corners with some strong shock cord to pull it tight. The Lynx is really the way to go if you want the best functionality. I went through the headache of making my own DIY Lynx clone which I am VERY happy with and keeps me warm into the 20's.