Compromises

There is some sense of the tail wagging the dog here, but,

• Thonk/Lamond end pieces don't fit my free rails,
• I already have the end pieces I used in The Cupboard,
• Those end blocks happen to be in the format of two pieces: four rails and two rails (that was done in order to get it into the cupboard),
• It would therefore be easy to cut the rails to width and use the 2-rail end pieces for the garage, then cut the 4-rail down to 3-rail and use that for the main section.
• Here's the compromise - using a straight 3-rail and rather than 2+1 would mean abandoning the elegant, classical 2 slopes and a straight (image from synthesisers.com)

Continuing the slope for three rails would, apart from aesthetic considerations, have practical consequences in that either the top rail would be very shallow or the garage would be too deep.

I shall have a ponder. I guess that if I have to cut the 4-rail end pieces anyway, I could cut them 2+1+1 rather than 3+1 and stick to the original design.