I have read numerous opinions on the cause of orange peel with dry (heat)mounting and do not believe the claims of surface tension of the substrate.

I have tried dry mounting photos (1 hour lab color prints as guinea pigs) on both matboard and Plexiglas (acrylic sheet for other non-brand products) at the recommendation of a local commercial lab who does this with PMA for high-gloss 'plastic' (polypropylene) prints.

It did not look any better (to me) on plexiglas so I don't blame the substrate entirely. It was a bit better.

I have never seen an unsatisfactory 'new' PMA mount coming from a commercial lab. By new I mean, for example, someone brings in a 'pro'
wedding or graduation photo for framing. Sometimes they are on nasty-looking mounting board that looks paper-based to me (why use '100 Year Paper' & mount to something non-archival?), and lately they are on a polymer board softer than acrylic.

As a framer, I personally dislike the look of drymounting of photos, especially glossy ones, but have to live with it because corners or hinges don't always work or have their own issues.

PMA is done with a roller press when one does enough volume to justify the cost of the machine. Otherwise a hard plastic 'squeegee'-like tool is used (analogous to a window cleaner's rubber-bladed tool, but less flexible).

You might want to experiment with prints you are willing to risk and try different amount of pressure. I don't remember, but I thought the 3M sales rep said that a mounting press does not create enough pressure for PMA application. Hence the other methods of mounting with it.

CODA is another brand of PMA (pressure mounting adhesive).

Murray