I like the concept a lot

Just be careful you don't tension the line on the front of it enough to bend the outer arms in. I will assume you spent the time to make the screw height adjusters even, and the length from axle to degree wheels exactly the same on both sides too.. (I'm not doubting you did, just pointing out possible variances)
If so, it looks like the thing should work great, as long as the rear wheel bearings don't have much play in them. If they do, try over-tightening the wheel bearings for the align

When you checked it, was it already in alignment? It looks like a great rig, and probably doesn't need much to maintain it.
One last thing; make sure the bars are perfectly level with the ground (assume level ground), otherwise, the measurements will be off...

Good luck! Post pics of the beast sailing when possible