Mosaic Tile - Backer?

[jgreatguyb]

I am doing a bathroom with the same 12 x 12 ceramic tile on the floor and the bathtub surround. At about eye level in the surround, I want to put an accent 6" strip of mosaic tiles. This mosaic tile is a natural stone square tile that come in 12 tile x 12 tile sheets (or 1' square) backed with a fiberglass mesh. The mosaic tile is about 3/32" thicker than the 12x12 ceramic I'm using .
To "ease" installation, a friend recommended I first mount the mosaic on 1/4" Hardiboard, let them set up 24 hours, cut out the 6" x 12" pieces with a saw. Then mount those 6x12 rectangles like individual tiles.
This would certainly make mounting the mosaic, square and straight, much easier. The problem using this technique is that the mosaic would sit too high above the surrounding ceramic tile on the wall, about 5/16ths of an inch. I could mount natural stone border strips above and below the mosaic, but the entire accent strip would still sit too proud of the ceramic.
Has anyone done this technique before? Is this too much extra work? If you have done this, how do you adjust for the height difference? I also want to lay this mosaic in a border around the edge of the bathroom floor. Should I use normal thinset to lay the sheets or something else. What about the height difference here? Given this project, how would you lay the mosaic on the wall and the floor? Any advice you give would be very appreciated. THANKS