Technically, dry mounting is not considered to be an archival conservation method for the very reason that it can not be 100% reversed. The reason for 100% reversal is the mount board and mat board get contaminated with harmful pollutants over time and this allows them to be replaced with fresh components. If you use truly acid free, and buffered mounting board, the dry mounting procedure is properly done, and the image is a few inches from the edge of the mount board, it will take a long time before the photo starts to degrade if properly framed. Bainbridge Artcare foamboard and mat board is even better because it will actively neutralize acidic compounds entering the framing package.

T-hinging with Japanese rice paper, and wheat starch adhesive is about the only conservative method of mounting artwork. Unfortunately, it will not keep the image flat. A slight curl to an image is considered proper mounting to a museum collector. To the average consumer, it looks like a poor mount job.

Unless you are limited on space (like many selling in artshows), I recommend 3/16 foamcore as opposed to 1/8. It is just a lot less likely to warp. Less of an issue for 16x20 and smaller.

I have more info about picture frame mounting techniques here.