The crack is not growing, so I am considering to modify it for a belt drive, just 1 gear, super light, for commuting. I would want to have some reinforcement welded over the crack, and polish the frame to raw aluminium. Medium term project.
I actually asked Peter about that (belt drive), and he was really down on the idea. A shame since I'm building mine with Alfine 11 hub gears and belt drive would've been perfect. If you do try this, be sure to report back here; I'm curious to hear how it goes.