As I understand it the only sled(s) that spacers are beneficial on are the red head 6 and 700's because of something to do with the way the reed port is molded,it doesn't allow the reeds to fully open up if I remember right.I have no idea whether they help on an SRX or not,I can't imagine they do as this isn't one of the mods that guys usually do on SRX's and believe me if they really helped deliver a hp or 2 or better throttle response you would no doubt see more threads on this topic.
Hope this helps.