23+ ktm seat cover install tricks?

I have just removed the plastic thing, stapled the cover on like normal and put the plastic piece back on.  I have Motoseat make my covers. We sell guts covers too. I've only installed our motoseat made covers on that generation KTM. But they work out fine. After you put the plastic back on it just squishes it. Other than the bolt hole , if Your cover is not made with it already. I would not cut the cover .

Putting the cover on inside a warm place and keeping it warm for a day or 2 after would also be recommended.  You can drape it over a base board heater , radiator or hang above a heat vent to get it warmed up a bit. But don't use a heat gun. If You feel that You need heat after You start installing, a hair dryer  would be the only heat source I would try other than the ones I already talked about. Get the cover on and let it sit inside by the heat. Do not let it get too hot. Keep it cool enough to be able to touch without burning Yourself and You will be OK. 

Get the circlip on as good as you can, and take a socket that goes around it, and give it a tap with a ball pein while pushing the plastic thing through the seat. Should seat the circlip into the groove

If you have an extra set of hands have them grab pliers and squeeze the plastic piece through the seat so the cylinder goes through and put the cir-clip on. Same can be done solo with a small c clamp. For future projects Guts Racing seat foam and covers have worked great for me on this bike and other projects. I'd avoid cutting your seat cover.

I just buy the optional ktm complete seats. Very happy I don't even know where my stapler is anymore 

Did that on my most recent cover. Well worth the (surprisingly few) extra $.