Yeah, it was happenstance on two levels.  First, I mis-measured the t-molding slot by about 1/64 of an inch...maybe less, so just a touch pops out of the t-molding.
Second, I didn't read all the way through the plexi shaping/building threads and didn't realize that a lot of folks polish the edges.  I didn't.  In fact, I think I'm going to put a slight chamfer on the exposed edge with some 220 grit on a block...very carefully...to make the edge lighting a bit more defined.
I might make some clear dust washers, too, since the joy holes are 45 degree chamfers, too.  
AJ
That is cool how the plexi gets edge lit.