The reveal is installed depending on the harware your going to use. J.

John - Using standard strap hinges and a gate latch, what gap would you leave? I can't see needing more than 1/4" on the hinge side and maybe 3/8" on the latch side. Am I underestimating?

With the design I want to use, it will be hard to trim it narrower once it is built. But, I don't want to leave huge gaps unnecessarily.

Here is a link that might be useful: Gate Latch

Use a cable with turnbuckle, run diagonally, to keep the gate square. Then your small gap will be good through the seasons. 3/8" is a good idea for the hinge side. The wider the gate, the more it will swell dimensionally drunig the wet season.

Ghesssssssssss.....get the harware, see what it takes, build the gate. Why is this so hard???

If you use the right harware and build the gate corectley there will be no sag rain or shine. J.