maxxII
Super Housemonkey!
I would suggest drilling holes in the rock pretty much anywhere you think you might want to stick a frag plug. Doing all of this (S-L-O-W-L-Y) while the rock is out of the water will give you all the coral mounting realestate you could ever want.
You can take a bare frag plug and size it to your masonry drill bits and get it slightly oversized easily. I went this route so that I could cut acro frags from their plugs, mount them to clean new plugs, (old plugs that I scraped everything off of and soaked in bleach then sun dried), and then if needed secure them to the rock via putty...
Just a thought.
I have no experience with Epo-Putty.
You can take a bare frag plug and size it to your masonry drill bits and get it slightly oversized easily. I went this route so that I could cut acro frags from their plugs, mount them to clean new plugs, (old plugs that I scraped everything off of and soaked in bleach then sun dried), and then if needed secure them to the rock via putty...
Just a thought.
I have no experience with Epo-Putty.