I'm a side sleeper too and I was uncomfortable with different 1.5" pads, but at 180 pounds no part of me was touching the ground. It was lack of a pillow to bring my head and neck up straight with my spine.

I got one of the small inflatable foam sit-upon pads, maybe 20"? Inflate it slightly and fold it over to double it. Made a small pillowcase with the open end on the length instead of the width and a drawcord. Put the pad in the case, stuff in my down jacket too, slip it over the end of my sleeping pad and cinch down the drawstring.

Now I sleep comfortably with a 1-inch pad, and the "pillow" doesn't slide away in the middle of the night.