I cut a sun shade to size and use it on top of the metal cover and under the carpet. Works great to reduce any noticeable heat. I cut a mop handle that fits into the side panels where it works to hold up the carpet when needed. The only bad thing about it is that there is really no storage in the car for it when not in use. (Maybe I should look for a retractable handle like used for some camera mounts to solve this issue and keep the carpet support rod stored inside the car when not in use). My carpet pad was cracked, so I repaired it by using book binder tape and that remains flexible and so far has seemed to work just fine. I only had red book binder tape at the time, so it shows more than I'd like, but it only shows when the carpet is pulled up to work on the engine, so no real worry. The book binder tape i used seems to not be effected by the heat to the underside of the pad and it has been in place of over a year, now and no peeling noted. (That tape can be purchased on Ebay in various colors and is not the same as Gorilla Tape or Duct Tape). The area where my plugs, coil bolts and such are located was modified on newer model Smarts to allow more clearance than my 2010 model is. Believe it or not, I had looked at the metal there and even considered making a modification by cutting it out a bit and being able to re-attach it with a couple of rare earth magnets and bracing when it was to be put back into place. The actual metal panel seemed to be easy enough to trim out without doing any structural damage in that area. However, I didn't want to do any alteration that may effect a future sale of the car. Being frustrated by that overhand and the tailgate in the way was not enough to get me fired up enough to do any body work modifications like that. I too have very bad arthritis, but the meds I am currently on have worked well for me so that I can at least tolerate this annoyance as I work on changing plugs or such in this area these days. Getting beneath the car and getting up off my knees is much more difficult than bending over the tailgate these days. That old mattress trick may be worthwhile to consider. I actually had more difficulty in replacing hoses and pushing them back into place so they didn't leak as my hand strength is not what it used to be.