Our M-382 (1979) has the traveller located on the cabin top (came that way when we bought it a couple of summers ago). The traveller car rides on a track which is bolted to a sturdy metal base. I've assumed the base is a heavy-guage aluminum, but I'm not sure because it's painted. This base has legs at either end which raise it to clear the cover over the companionway hatch. The legs then are bolted through the cabin top. I'm not sure what kind of backing was used since I haven't removed the headliner in that area.
This base, or bridge, for the traveller is located just forward of the companionway. The mainsheet block on the traveller car has four sheaves, spreading the pull to two blocks on the boom which are spaced maybe a foot or two fore and aft of the traveller car.
My previous boat, an O'Day 25, had its traveller on the bridge deck in front of the companionway, and I really like not having the traveller in the cockpit. Not only is it out of the way, but I think that the mid-boom attachment probably gives you better sail control.
The only thing I don't like about our setup is that the traveller control lines exit their clam cleats facing forward, so I have to go up on the cabin top to adjust the traveller. If I can figure out a way to bring them aft through or under the dodger, I'll turn the whole track end for end to solve that problem.