Hi John,
Our shop has been using red and white oak for braces for nearly 20 years and YES, it does shrink and doesn't look pretty if you put them in green. We also learned the hard way to use free of heart center (FOHC) stock exclusively.
Our solution, since we are in the business of cutting up frames, is to buy our brace stock at 3 1/4" x 5 1/4" minimum green. Then we put it on sticks and dry it for as long as possible. We shoot for at least a year, which in Ohio leaves a nearly dry center. When it's time to cut braces we sort through and save the really nice straight stuff for handrails and saw the rest into brace blanks and plane them to size.
One word of warning is you don't want a really tight green timber brace mortice with a nice dry (pre-shrunk) brace in it, so we cut our braces with a little bit of slop (undersized tenons) so they don't force a check to start. The pre-dried braces stay looking nice and hold their 45 degree angle well.
I wouldn't worry too much about the ones that are in and have shrunk. They're probably still doing the job just fine. We have several nearly 20 year old frams out there with the same problem and none are falling down yet. The hardest thing of all is to quit looking at them and move on.
Good luck with your work.
Rudy
