Pegs:

Metal templates will be strong and durable, but I would not make the base plate out of metal, as the bit is likely to come in contact with it. Perhaps a metal framed template would be stiff enough with just the walls, and without a base, and the router could ride directly on the timber. This is better anyway, as there will be no hole in the center of the template for the router to fall into. With the fixed size templates that I've been talking about, only half of the router is supported by the template base, and the rest floats over the housing. This is why you can only route the perimeter of the housing. If your router rides directly on the timber, you can remove more of the housing with it. Just leave some "islands" for your router to ride on. CB.