This evening I trimmed the J-channels. I found that using the 11/16 and 7/8 dimensions left the tabs slightly too short. Being concerned with edge distance, I trimmed away 1/8 inch more (to make the tab 1/8 inch longer). That was actually about 1/16 inch too much, but the extra will be easy to trim off later. So far I've only done the aft ends of the J-channels. I'll wait until I'm working on the F-707 bulkhead to trim the forward ends. I also started working on the fit of the F-779 aft bottom skin, but didn't get too far. I was too chicken to really start bending on it, so I decided to do some internet research to see what others have done.