So, what actually is it? A kart, a bike engined race car or.....
There is a specific kart forum, if it fits in there, or maybe Racing technology, or even track day forum may get more response. I guess like me, not a lot of people on National & Club Racing know what you are talking about!
As for slipper clutches, my understanding is that they are usually fitted to protect the drive train
wheel side of the clutch, not engine side. If you are over-revving on down shifts, that's surely down to driver to adjust technique.....
Edit- just googled 'Speads RS08' so at least know what it is, now! I see you've asked the question in 'bike engined race cars as well'.