I have a dry press and a friend of mine has a vacu-seal, sometimes we get great results but more times than not the images end up with hot spots even at a low temperature due to the metallic paper.
We have both found that the ones that give us problems are the images that have alot of red, black or gray colors in them.
I now inform all of my customers that I will mount them, but I make them sign a paper stating that hot spots could occur and that they take responsibility for any damages that might occur, that if a problem arises that they will need to pay for a new photograph. I also tell them that they need to have any future images mounted at the time of printing. That if something happens at that time the company just prints it again. I have contacted mpix (one of the main sites that uses metallic paper) and was told that the proper way to mount these types of images are to use a roller press and self adhesive boards. This is the method that they use.
I still have people who want me to mount them and I have good luck about 50% of the time. This is just my experience with these types of photographs. Hope this helps.