I painted the two lash ups with my everyday satin Black from Wilko, they will have to sit in my living room while testing, so they might as well look tidy. Its water based Acrylic paint so I thinned it down with a little water and used a roller. It soaks in well when thinned, acting more like dye than paint. The holes all lined up so the drivers fitted without issue.

The rear view shows the plate for clamping the tweeter and the cord restraints for the leads, which have banana sockets fitted.

Close up of the clamping method, using "T" nuts and non magnetic machine screws.

The wave guide looks to have a chamfered entry in this picture, but it's actually a full quadrant with 12mm radius.
The original face plate has a 33mm dia hole, so I used a 33mm hole saw, then a 12mm round-over router bit, but ended up with a 33.7mm Dia using this. It fits well enough though.

The completed assembly.
Spacing of the drivers is pretty close to how it will be in the final build and the volume of the closed box is the same 55L.
Initial sound, just dialing the drivers in by ear, is pretty encouraging, I used crossover points on the Hypex DSP of 450/5000 Hz and the tweeter inverted.
I need to take some measurements now and do the job properly, which may take some time as the Christmas Holidays will intervene.