Is it possible to somehow mate the liner to acrylic?
Some way to weld them together, even with additional bracing would eliminate the problem.
That way, the front would be a peice of acrylic and just the two sides and bottom would be welded/molded to the liner.
"Maybe" you could have an acrylic manufacturer make up panels for you, with a strip of your liner molded into the acrylic on three sides.
If it were say, a 1 inch thick panel, and your liner were molded into it one inch, with a U shaped overlap, I imagine that would be quite strong.
If the sides were supported and angle bracing for all corners the full length of the panel, then there would be very little pull against the seams.
This is kinda what I was thinking, but instead of welding the vinyl to the edges of the acrylic; enclose the acrylic in two layers of vinyl. Bond the two layers of Vinyl to each other just outside the edges of the acrylic, after vacuuming the air out of course. Kinda like laminating a card.
some what.