I did my entire cab and rear floor. I have a thick rubber mat in the back too, but I just took it out, SC'd the floor and put it back on. The cab was the trickiest bit. I may have gone overboard covering every single inch, but its a 204. I can handle the additional mass. I'm assuming your thick rubber mat is glued down. Mine was removable as was the thick plush foamed carpet in cab. The thick rubber may act as an insulant in a thermal sense, the purpose of SC is to reduce high freq vibes and to attenuate noise ingress. Thermally, i have access to a variety of products in my industry. I intend to maybe investigate something fancy. Some VIPS. (Vaccuum Insulation Panels). It may or may not be suitable, but I am not going to freeze my tits off like we did in our old T2 moneypit. Anyway, once I get the interior hardboard panels off from underneath the carpeted rear I can assess if theyre possible. If anyone else here has looked into this, I'd be interested.