Just weld on end pieces to change the strip of acrylic to a channel of acrylic. Even 1/8 inch thick acrylic should work fine for that, maybe .5-.75 inch wide strips.
That was the thought. I cut them at one inche because I don't trust my fingers on the tablesaw with much smaller cuts. I'd hate to look like my old shop teachers.
Upside down U is I guess the shape I'm going for on the top piece.
Only reason I tried without it was I didn't want to hinder airflow to the LED heatsink.