I'm a bit suprised that many have not seen work before with a float mount. Adams work is presented this way as well as John Sextons. I mount both ways, float or linen tape behind an over mat. If it is for a sale, the float mount is what I use with at least a 6 ply mat. For exhibits and other uses, I will tape mount because it is a lot less work than doing a really good float mount and allows reuse of mats.
The Ansel Adams photography book, the red paperback book, give very good instructions for dry mounting and matting with floating mats. I found the advice about making jigs from mat board and using a draftsman's weight bag to be very helpful.
With certain types of dry mount adhesive (the type which completly melts) the edges can be self trimmed. The proceedure goes like this.
Place the print face down on some kraft paper and cover with adhesive larger then the print,
Place in press between two pieces of relese paper,
Close and lock for 30-60 seconds,
Open and remove assembly,
Quickly seperate the sheet of release paper and the kraft paper, the excess adhesive will cling to the kraft paper leaving the print clinging to the other release paper which can be removed when cool.
Now you have a print with adhesive on the back perfectly trimmed and ready for dry mounting.