The figure eight loop knots at the ends of my Spectra rigging are tightening and causing the rig to loosen up, so I've been adjusting them after each sail. I've also moved the shroud attachment points 4" (100mm) farther aft for better support on broad reaches and runs. I do this so you don't have to :-)
The GPS is showing a true 90 degrees between tacks which is better than the other rigs I've tried on canoes. I guess there is something to having a tall narrow rig for going upwind.