Supplemental Pad Question

[HillbillyHanger]

I'm going to try my 3/4 underquilt this winter with a supplemental pad. I watched the video that Shug did on top quilts showing his use of the Thermarest sit pad. Is one supplemental pad with your feet sitting on the pad typically enough pad for partial underquilts? Do you ever have to use a longer pad and turn the pad up (against the end and the bottom of the topquilt footbox) so that the bottom of your feet and your heels are on the pad?
TNX

[Red Wing]

I would buy a roll of standard reflected for 15.00 and cut a piece long enough to overlap your uq and the shove it in your foot box. Easy peasy