Glad I found your thread TWS.
I use Hardware cloth for gopher prevention. I had gophers in my garden 2 years ago, they got 2 of my plants. I had half ass gopher prevention, but they got me.
Last year i made individual "cages" under my 3'x3' 12 inches high wooden raised beds. So it looked like another 3'x3'x1' wire box under the wooden raised bed part with the wire going up the sides and attached to the sides of the raised beds. I did 3 like this, then ran out of hardware cloth. I used half inch chicken wire on the 4th box, it was still invaded by a gopher and that plant died.
Half inch hardware cloth is the ticket, expensive, but well worth it.
TWS good idea about putting pots in the ground, keeps them cool in the summers heat.
If I were you I would just grow 4-6 in that 12' x 16' area in the ground. I SCROGED 4 in my 16' x16' weed cage last year, I lost 1 (mentioned above) tgo gophers and pulled 7+lbs from the other 3. I would SCROG 4 girls and grow MONSTERS. Use your "Super Soil" in 4 holes, but rototiller in some goodies in that greenhouse area. You can grow 4 FAT BEAUTIES in there, that's what I would do.
I'm subbed...
TMB-