Here's what I did and it works great.
I went to Lowes and bought some dark gray indoor / outdoor carpeting. For 20.00 you get much more than you need.
I laid it out and set up the set. The important points are the bass drum spurs, hi hat legs and at least one or two of the throne legs (to keep it from sliding). The rest of the set needs no carpeting underneath. Since I don't sit bass drum front, but rather off to the side so I can face front, I cut off a bit at an angle to indicate to me where I want stage front to be. Whole thing ended up being about 3'-6" x 4'-0". I use either a 22" or 20" bass
I then taped it off, removed the drums, and cut. I got two drum rugs out of the piece I bought at Lowes. It's extremely light. I fold it up and it goes into my hardware bag (last in, first out).
Seriously, it weighs less than a pound.