2' x 6' only weighs 6oz. I read that it will add about 10 degrees to your sleep system. Using it instead of my Nemo Tenslor I will save about 11oz. My base will be around 6 lbs with it. wondering when ultralight becomes ridiculous. Right now I am pretty comfortable at night. My pack is a Osprey exo 38, pad - Telsor 25, Bag is an EE Revelation ( 20 degrees )Tarp - SMD Deschutes plus. I know if I go with the reflectix pad my comfort level will drop. Wondering if 11 oz is worth it. Going to try it on an over night next week

Chances are you'll deal with it for a while and then add some comfort items back in.

I've used car window shades, essentially the same thing as Reflectix, to supplement my pad, but never to replace it. Except once in a hammock, but that was a cold restless night. Granted, it was in the mid 30s F. Try it in your yard if you can. What have you got to lose?

I haven't used Reflectix, but have used a similar product called Low-e Insulation under my pad. I think that it improves the heat retention, but can't say for certain. It is too thin for me to be comfortable using it alone.

You could try it at home first.
Put it down on the floor and see if it works for you for more than an hour or so.
That is of course if you don't happen to hike where forest duff is there for the taking.