i love the changes you made to the Kadet.

The loosening you had while doping is not from brushing, it's from the brand of silk you are using.
Thai silks seem to be pre shrunk and don't have much shrink left in them, I only use that brand silk on solid or sheeted areas now.
As countilaw said Dharma silk is better for your open framework because it will shrink more than Thai silk.
I started with silk from Thai silks and switched to Dharma Trading and I've been happy ever since.

Bridging is caused by the dope shrinking and pulling away from the two surfaces. that is a good place for non tautening dope.
I keep a small bottle of clear butyrate that has a couple drops of castor oil added to reduce shrinking on the bench just for those areas, it helps.
Looking forward to more pictures and updates.

buzzard bait, your plane looks great, nice job.
Paul