Adding in underquilt with insulated pad to prevent cold shoulders/knees in Ridgerunner?

[meteorharry]

I'm really enjoying using a long/wide Thermarest X-Therm Max in my double layer Ridgerunner but do occasionally get cold shoulders/knees when I side sleep and I end up rolling near the edge of the pad. Does anyone have experience with adding an underquilt to this setup to try to prevent drafts along edges of pad? If so, was it effective? The width of the underquilts from Warbonnet and Arrowhead are only 30"-32" so I'm wondering if these will really give enough coverage along sides when I'm elevated on my already 25" wide pad. It seems like the underquilt would need to wrap the Ridgerunner up to nearly the level of the bugnet zipper to really block cold from sides.

Btw, I've also played around with adding reflectix or CCF on the edges but then I have to move the pad to the top layer (instead of in pocket between layer where it stays put) to keep the reflectix/CCF in place and the pad moves around more than I'd like (I'm an active sleeper).