I've never made a secret of the fact that I consider the PC style template guides as museum pieces. Makita and Hitachi, whilst not compatible are made from steel and until the current Makita RP2301FC were held in position with two screws. The Makita which uses the same guides, fits and locks in place with the pull of a small lever. Guides up to 40mm are available and even bigger ones can be made. Unlike James, on two occasions of the very few times that I've used the Brass guides I have plunged too low and the guide has unscrewed! Shown also is a set of five home made one piece metric guides, 20,25,30,35 and 40mm.
It has been suggested on this forum that steel guides are dangerous as if a bit hits it, it will chip. In the forty years that I have been routing, the only bits that I chipped were ones that I dropped onto the concrete floor! For maximum depth of cut, and that is what we all want, the chuck must fit through the template guide.
Nothing but heaven itself is better than a friend who is really a friend. - Plautus