Fitting a Cat Eliminator
has to reduce
under-body heat, simply because Cat
Converters are
heat generators, designed to generate sufficient heat to get the catalyst honeycomb up to at least 600°C before it'll do anything in the way of 'catalysing' any exhaust gases!

So if you remove that heat generator, you WILL reduce a significant amount of the heat generated and radiated immediately underneath the bodywork, engine, and seat; and instead, you see most of that potential heat get blown out the back with the rest of the exhaust, somewhere which means that heat cannot spread/radiate into the rest of the Spyder.
As to how much heat that'll actually reduce in
your seat, &/or how much it'll '
help with seat heat', your guess is as good as mine, I've never bothered to measure it, and I have no idea what might be causing
your particular seat heat issues.
BUT, I can tell you from my own personal experience that on my 2013 RT,
fitting a Cat Eliminator certainly helped reduce MY seat heat issues!
I
know this, because
BEFORE the Heat Minimisation Recall came out & was fitted to my 2013 RT, and
before I took off the Catalytic Converter & installed a Cat Eliminator, on a warm day, besides the blast of hot air from the Dragon's Mouth RHS radiator vent onto my Right Shin, I simply could not sit on the
seat while riding for anything much longer than about an hour, hour & a half at most, before the seat became too hot and besides my butt, certain other more sensitive parts of my anatomy became
VERY CONCERNED for their future ability to function/contribute any further to the gene pool!! And every other (male) rider who rode my Spyder for any length of time complained of similar anatomy cooking issues.
Yet
AFTER I fitted the Cat Eliminator, and still before the Heat Minimisation Recall came out & was fitted, I (and others) could
easily and comfortably ride all day on that same seat because it simply didn't get anywhere near as hot - and at that stage, the
only thing that'd been changed was fitting the Cat Eliminator instead of a heat generating Cat Converter.
So for
ME, yes, fitting a Cat Eliminator certainly
CAN & DID help reduce Seat Heat! YMMV, but it made a
BIIIG difference for me/my Spyder seat!
Just sayin'
