You could get a sps that is a VERY slow brancher...The GARF purple bonsai is known to be a sps that encrusts as much as it can, before it starts branching. Heres mine when I got it 8/3/12, and a picture from 5/22/13
In 9 months, the branches have not grown at all, although, I do have a third .5" branch developing off to the side thats not in the recent pic. But still, all the growth in 9 months has been encrusting. Its like a cool putple/green polyp monti =)
Other corals (example shown) have grown branches significantly in less of a time period, so I know my conditons are good. The bonsai is just supposed to be a slow grower if you give it some space to encrust (mine is starting to encrust off the rock onto my