I typically like to put stags at the bottom near an open space where the can branch and grow - A. Youngei can/will be growing out of the water before long if you do a good job.
Light and flow has never mattered too much in my tanks, but I have plenty of both.
pick a small piece of rubble and use a rubber band to attach it. it'll grow into the rock and then you can put it where you want it. i have one on the sand bed, he's grown a lot in the last couple of months.
Did you use a 2 part epoxy and get some on that spot perhaps? I see some purple specs that look like it.