I only used one aluminum hammond chassis to make a head . It's easy to work with but I just mounted mine on the bottom of the cab tubes facing up and drilled holes through the bottom sides where they flod in and have about a 1/2" lip. Trouble is the aluminum does not due well if the tranny's have any weight to them . I also used those metal clip nuts that slip over and around the aluminum edge so you can use a sheet metal screw and not depend on the aluminum to hold the screw threads. This is the head .

The back panel removed goes down to the chassis and has two cutouts like the tweed fenders for cooling.

Later I changed the head into a parallel SE and used the black metal chassis , harder to work with but the end result is stronger, They also sell the bottom cover plate for both and this helps.
I also used a black metal one for a tweed style chassis in a cab I built . I just drilled into the corners like fender did and used a large machine screw and inside the chassis top corners a washer and nut but still added side support to the bottom sides to keep it from bending and flexing . To support the bottom from flexing I drilled through the bottom lip and used the clip nuts and drilled through the back cover panel so once the back panel was in place and the two screws inserted it was pretty solid . If it's tweed style like Slucky did also works and that way you don't need to worry about the screws touching any of the tube sockets or wires. I kept mine spaced so they would clear and short enough so they didn't go in very far.
I prefer the metal hammonds they have a sort of black krinkle finish which lends well if you want to do a faceplate with lables . I used the type of decals that are for model trains and planes you can get numbers and letters in any size and in gold or white . Microscale makes them . You set them in water and then they slide off and you set them and can move them into place then once dry use micro set or solvset which allows the decals to soften and hold on for ever and allow the decals to melt right into the paint and once dry the decal film cannot be seen they look like they were lazer painted on. Most hobby shops carry them of on-line . All you need is a very fine pointed 2/0 of smaller model paint brush. They work great. They only seem to work on painted surfaces.