I tried them 2yrs ago on a friends advice. At 13yds the ST just stuck into the shoulder of a large 8-point. We found the broken arrow,only 2" went in. My friend agreed the muzzy's I normally use would have gone right on through.
I'mcurious how much kinetic energy your set-up has. You can figure kinetic energy by taking the arrow speed X arrow speed X arrow weight divided by 450240. Just curious if low kinetic energy had anything to do with the lack of penetration when you hit the big bones of the leg/shoulder!