Italuminum,
I had many issues to work through as well...and I did end up using off the shelf tubes from Rock West Composites. All my notes are at my shop (so is the bike) but I'm certain I used the same size tube for the top/seat tubes (1.4 OD?) and used a bit larger tube (1.625 OD) for the downtube. I just used the standard .065" thickness tubes. I had some tell me to use a thinner tube, but for the minimal difference in weight and the added safety factor of the thicker tubing, I thought it was the way to go.
My biggest issue was getting the geometry correct with the 650c front wheel "curve ball" thrown in. It looks right....but I'll see how she handles when I ride it for the first time tomorrow.
Here's a few more pics...
