Pretty meh, tbh. The hole where the shaft of the Sam goes through the harness is SO tight and small that I was terrified I was going to rip the silicone of my dick putting it through. Some of the stitching ripped as I eased it though, too. The pressure of the tight hole closed the shaft of the STP a bit.
Also, while the design means that the Sam is in the right spot for STP use, it also means that you have an STP between your legs all day which is extremely uncomfortable. You also have to bend the shaft of the Sam in half and tuck it into the elastic band on the harness so that you don't have a raging boner.. but this is going to tear the silicone in no time.
Not the greatest design, imo, but perhaps it will work for others.