sling pin, 30g is SLOW to push and makes my thumb hurt. 27g is much better and easier but I would not try to draw through it. i draw with 22g. 25g works but it's slow. I typically pin with 25g but of course 27 is nice.
i draw with 18g and back load the slin pin. really nice for delts, pecs, calves, etc. mine are 29g.
oh and if it is hurting your thumb that means you are not working your thumb out enough...j/k...