Flooring Tile - Installing porcelain shampoo niche

I am about to tile my shower. I had originally wanted to have a recessed niche, but all I found were the tile-over kind (like you see here (http://aquafit-usa.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=AUCT&Product_Code=REC-1418&Category_Code=R)). The dimensions are a bit to big for my framing, and I didn't want to deal with cutting tile to cover the niche.

Fast forward to this week when I picked up my tile. I found they had a discontinued porcelain niche like this one (http://www.tiledepot.us/bathroom-accessories-171/niches-and-benches-porcelain-152/recessed-shampoo-soap-porcelain-parchment-glossy-small-1063.html) that they will give me for $20. I won't need to tile over, the color matches my tile, the dimensions are right to fit between studs, and the price is right.

I am curious about how this installs. Can I just cut the backer board and put it in w/o any cross bracing? Is it just being held there by whatever adhesive I use to seal it to the tile under the flange?

Thanks!
~john

The narrow design will almost require sub framing. I am assuming your cbu is up already. Cut the cbu to the dimensions indicated. Place cut 2x4's on top, bottom and sides, attaching them to the cbu with proper screws from the face. Apply Redgard on the exposed wood and the wall behind the unit. Others may not deem this necessary, but it is a small expense for a little peace of mind. You probably won't be able to secure them to the studs on the sides. This will stiffen the opening. From what I can see, you would apply your tile, leaving the opening, and siliconing the unit over the tile, then silicone the outer edges, leaving a 1/4" open space at the bottom edge as a weep hole.