Looks like a good start, Tom. I've built a Solsylva, and you can get good results with them.
Do yourself a favor now (if you haven't already done so) and lay a straight edge along the top of the pipe rails and make sure that there is no light showing between the straight edge and the pipe, and also make sure that the pipes are pretty darn parallel with the surface of the box. When you torque the pipe mounts, its very easy to introduce gaps that way.
Look forward to seeing more of your build!