I've been browsing local plywood shops in the hopes of finding a local supply in Portland, Oregon.Regarding 1/4" for ribs on a Maupin Woodstock sailplane, Douglas Fir was called for. Here are my local options and looking for opinions and experiences with these:1. 1/4" marine grade A-B Doug Fir : I found it to be much more flexible than anticipated.2. 6mm Aquarek marine ply : uses mahogany I believe.3. 6mm Okume marine ply 4. 6mm Hydrotek marine ply5. 1/4" Russian Birch ply : very nice ply using exterior grade glue and appears to be about grade A-B. Not finding evidence it has voids and some 4x4 sheets had no patching at all.That's what I have found locally thus far. I know I could pay $$$ to have stuff from Aircraft Spruce but want to evaluate my local options.Who's got their 2 cents on these?!