I use SD1 and Sd2 boleros a lot. Never broke a head, got blisters, or dented a head. If you have to hit so hard that your head dents, you are probably using the wrong stick. I would raise the drum, and get a heavier stick and let the stick weight do the work. Sd1s are maple, and lighter than hickory. Try a 2B or something in between. If technique is right, you should not get blisters. You are holding way too tight, and are not using fulcrum effectively.