I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

IMG_4517.jpg

The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

Thanks as always,