I had an SPS and it shot quite poorly. Had a bad barrel. Would throw the first few shots out of the group, then settle down. Until you allowed it to cool a bit....then it started all over again.
Thought it may be bedding, so gave the glass stock, (I think an HS Prec?) with bedding block, a skim of acra-glas. And a goodly amount of glass at the recoil lug area.That helped but still tossing shots.
Replaced the trigger, which helped as well.
Finally rebarreled and it was a solid .4" shooter at 100 yds. I think the original barrel was not stress relieved properly. Consistently threw the first 2 shots left and high.
I like the short barreled SPS configuration. Light and handy. I put a longer Hart 1 in 8" tube on, but the same contour.
Mine was a bit of an anomaly as generally the SPS's shoot quite well out of the box.