I'm with Daisy on this one.

Your first priority is to take what you need for the worst reasonably-expected conditions. After you do that, reduce weight by gettting the lightest version of what works.

So, in this case, an adequate R-value is your first concern. I camp in those general temperatures, and I find that it's not unusual for a predicted 2C to run toward minus 2C, depending on your choice of campsite and the wind you're exposed to. I tend to go with an r-value of 3-4, unless I know I'm going to sleep on snow - then I want something more toward 5.

You can find such full-length pads that weigh less than 450 grams (the r-5.7 NeoAir XTherm, for example.)