The problem with a less than full scale mock-up is that you will not see what the speakers are actually going to look like or how they will fit.
I thought that two 12" H-Frames at 16 1/2" wide each (not counting the plinth) would not fit in the space I had available so I went with 8" H-Frames. After I got them done and installed I realized 12" H-Frames would have fit. They would have been tight, within a couple inches of furniture on either side, but since the H-Frames have nulls to the sides that wouldn't have mattered.
At that point in time, not having heard either the 8's or the 12's and especially not a comparison between the two, I might still have chosen the 8's but that's not likely since the price difference is negligible.
On the upside, I have now been able to directly compare trip 8's and dual 12's.
Mike