Each side of the feet has a dado to accept a spacer that ultimately helps keep the struts equally spaced and parallel with each other.  I want the outer face of the spacer to be roughly even with the outer face of the struts once they're installed, so the spacer need to be about 1/8" thicker than the structs to account for the dado depth.

(This photo was taken prior to sanding the struts down to 3/8" thick.)

The end of each spacer also has a taper.  My first attempt at making the taper was to mark the angle on the edge, cut the bulk of the excess away with the bandsaw, and then sand down to the line.  This worked, but it was time consuming and fiddly to sand an even angle.  I did this for two of the spacers and then scrapped the technique.  Instead, I'll assemble a quick tapering jig for the table saw.  It would be quicker and yield consistent results.

All spacer blanks are ready for their taper, which also includes the two that I had already done.  (When the thickness of the spacer was reduced to account for the thinner struts, the taper angle changed, so they needed to be re-cut.)

For the jig, I grabbed a few scraps and glued it up - a piece of 1/4" plywood for the base, a stop at left side (the excess will be trimmed on the table saw), a piece of 3/4" plywood for a fence, and a scrap of cherry with a square edge to ensure the fence is vertical.   The end of the taper is left 1/8" thick to just fill the depth of the dado.

The taper is so shallow that there's no easy way to clamp the work to the fence and avoid the table saw blade.  Some double-sided carpet tape worked perfectly to stick the work to the fence.

I selected the best side to face out and marked the end that would be tapered.

Yeah, that's much better. 

With some final sanding, on the feet and spacers, they were ready to glue-up.