constructing panels

I have decided my painting substrate will be cradled wood panels. For the past week I have been working on perfecting a couple. I used 1/4" birch plywood, braced with 1 x 2's- panels are 11 x 14" and 12 x 16". But I only used Gorilla Glue to join the mitered corners and to apply the frame to the panel- first mistake. Then I applied like 6 coats of Gamblin Traditional Gesso only on the front. I sanded in between coats and the final surface is amazing! It's like an eggshell. Seriously. It's gorgeous! I just keep running my fingers over it because I love the way it feels. And then- I woke up this morning and the panels had, of course, warped- so much, in fact, that the mitered corners split. So there's that. I am trying to salvage them. I've got some heavy duty clamping and screwing and glueing to try. If that doesn't work- I'll try a turnbuckle to unwarp the front. In any regard, I am going to construct a couple of new panels and will take more caution with the next batch. I am also going to use maple ply- which is a harder wood, so I'm hoping it won't warp as easily.

Oh the frustration!