After examining an issue several RV-8 owners have reported -- cracks on the lower cooling ramp, aft of the firewall -- I decided to install some special vibration-deadening pads on the inside of the ramp. The stuff I used is called "Dynamat Xtreme." Teenagers use it to stop rattles in the door panels of their cars when they crank the volume of their stereos up to "11." You can buy Dynamat online, or at Best Buy. It's not very heavy (less than 0.3 lbs for my installation) but it's very dense. For an RV-8, all you need is the "speaker kit," Part # 10415, which consists of two 10"x10" sheets of the stuff. (Not sure how much you'd need for other RV models.) Once you get the backing sheet off, it's REALLY sticky, so make sure you place it correctly the first time. I covered the entire skin, plus the stiffener that runs across it. This stuff really does deaden the skin when you knock on the outside, as compared to the adjacent skins. Hope it works. Can't hurt, I suppose.