Stud mounts into Alumalite is NOT the best situation. Stud mounts are designed for solid substrate (bricks, wood, concrete, etc... ) that allows the studs to be inserted into. The hollow core of the Alumalite will not allow the adhesive the hold to anything.
you are better off with a solid dimensional letters, like mentioned acrylic, and use VHB & silicone for installation.
Why was Alumalite speced for this
sign? you are dealing with (what now appears based on the details) a high end pole
sign.
Alumalite in our experience is VERY easy to dent the surface. DiBond is a MUCH better substrate, comes in 3MM or 6MM thickness. Still use the frame idea with
signs on each side