Here are some pictures of my '37s. I've had them for about 6 months. They were worn on-and-off for the first 3 months, and then pretty hard for the last 3. They've gone through one initial warm soak and two cold washes.
on oipolloi's site it says you should dry clean only since the fabric is shrink to fit but in doing so it will fuck up the zipper and it will be all jacked up?
I can't speak for the 551Zs, but I owned a pair of Samurai 505s before and they had a zipper with unsanforized and after I soaked/washed them the zipper still worked fine. It just may not zip as fast as it did because you start to get a little curving of the zipper teeth along the fabric.
Right now I'm looking at a pair of LVC 1944 501's and I'm having trouble which size to get with these. My Crate Route's in size 33 are a perfect fit for me if that could be a reference point. The measurements are the same minus the higher rise on the 501's. Should I get the 34's in the 1944s?