Your stabilizer should tell you how many stitches it supports. A medium will support about 8,000 stitches. I was also told to starch heavily and to use an iron on interfacing - in addition to stabilizer. This was after I had used 3 or 4 tearaways for a 30,000 stitch project
- which of course wouldn't lay flat. Since using starch & interfacing I have had much better luck and on heavy stitches 30,000+ I use 1 medium tearaway & 1 cutaway.