Mounting plates...

Mounting plates with circles cut, ready for gluing

Here are the mounting plates with the coupler and speaker mounting circles cut out. They're made in two halves and glued together to make the whole plate. Gluing is currently underway in the garage :-). They are then cut around the outside to make the appropriate shape.

Update: The following day I discovered I'd not clamped one of the plates very well, so the two parts had slipped and got out of alignment. So I made a new one today which took much less time... Except  that in the rush (rush!! Ha!) I forgot to cut the clearance slot in the edge of the lower half to allow for the tightening clamp of the rubber coupler. Bugger. I can fiddle that though, and it doesn't show.

Moral? More haste, less speed. Enjoy the trip, dude.