Your trying to put a 2 inch peg into a 1 3/4 inch hole. It is a tough fit. The soft blanket can help. But does not stop the bell housing for getting you. The Hard (metal) covers have the same problem. Carbon fiber (glove type) generally work with alum. drums. Steel drums can through them. Going to billet steel drums does help greatly. However not fool proof, all it does is raise the rpm point until it lets go. And by raising the bursting point you also increasing the energy it is going to release. Resulting in an even bigger explosion. Anything you do for safety with these is likely and will increase the heat. Fix it! Install a large enough "separate with fan" external trans. cooler to solve the problem. Now as for the 904. We all know that the physical parts inside it are small, right? Due to their small size they will have less inertia, with this lighter weight it raises the rpm limit that they explode at. It takes a much higher rpm to reach its bursting point. It is slightly higher than billet drums. So, ultimately the 904 also has a limit also. ULTIMATLY it's not about what fits. It's about what you can put under there to protect you if it happens to you.
