Yeah, the CF works great for bashing & racing. I have the Fullforce 3mm CF plates & they have held up so far. I've had my savage land & crash on several 10 ft drops & haven't had a problem yet.
Here is a tip when you are done making them. Before you put them on, take a Q-tip & put some CA glue on it. Then run the Q-tip along all of the edges of the CF. This will help reinforce the CF plates from spitting.
I think you would definitely be fine w/ 4mm. I wouldn't go any less than 3mm thick, b/c I've seen some 2mm ones crack on hard jumps. Since you are making it yourself, you might want to make an extra set in case you do happen to crack one. Other than that, go for it.
Later....:mex: