I'm partial to Therm-A-Rest pads, but this can apply for others.
It's pretty involved, so be prepared.
The top two charts are for 3/4 and full length sleeping pads, respectively, based on R value per weight in ounces.
The large table is for the lightest, warmest, and most logical pad combinations, based on R value per weight in ounces. It is followed by an organized list of pad combinations in order of R value.
Highlighted in the tables are my personal pad selections, based on season, weight, warmth, and if a 3/4 length, full length, or combination of pads is desired.
If you have any questions or comments/insight, let me know.