Hi David, as you would be aware that style of bridge is normally used on solid body electric guitars. It's mass does not allow it to work too well in an acoustic situation. It is also made to be screwed to the top surface of a solid "slab".
With your acoustic build, you mention keeping the gap between neck and top, you will notice a lowered volume and tone, I would expect.
To answer your question though. To mount the bridge you will need to reinforce the top in the area of the bridge with a block that the bridge can be screwed to. If it were me using the bridge, and I have a few, I would put the bridge at the end of the box and use a larger tail block to mount into. I would then worry about plotting the scale length and neck position. This method would allow you to keep the space under the top.
Hope this helps. Taff
A thought but something I've never tried. Secure a block of wood under where your bridge will be to the back of the guitar. Keep it about 1/4 inch shy of touching the top. Pre drill and screw through. Other than the four anchor points your top should be free to vibrate. Also if you make the block bigger than needed it will give you swing room. Allow you to line up the bridge with the neck.
Also a tip. Because i've seen so many people use these things for nothing more than a decoration. Measure your exact scale length. The grove in the saddles should be at this point when they are about fully extended forward. Attach bridge to guitar. Then adjust intonation. Because you will always go backward from the scale length.
I usually glue a 1/4" piece of hardwood under the bridge for the plate screws to anchor in., The gap you speak of is adjustable..,I usually use a banjo style neck thru, and this lets me adjust the gap.,., from 0 to about an inch and a quarter max., build #145 in my pictures uses that style bridge, though I put a riser under the bridge plate as well.,.,