The RS Shocks mightFIT an RT, but I doubt they'll work very well at keeping the front end under control &/or off the ground under load or cornering! RT's are somewhat heavier than RS's and even with their OE 'heavier springs', are generally pretty much very close to UNDER-sprung as is.... I'd hate to ryde one much further/harder than a gentle 1st gear tootle around the block with an EVEN LIGHTER set of springs'n shocks up front, no matter how much pre-load you added!!
As mentioned, there is 'Fit', and then there is 'Function'. Fit - Yes, Function - No. Without function, it's a no-go. They will work on the later model RS/RSS and ST Spyders though. I believe the overall length is something like 3/8" shorter than OEM for the 2013+ models. Frankly, not enough to make any real difference.
I've run these Progressive shocks. And I used to sell them also. They are excellent units. Certainly better than Fox, probably not quite as good as Elkas.