OK, it's been a while. Way too long actually. I finally purchased a package of carbon paper - the last package Staples had - and now have enough for about 50 instruments. This morning I used it to fit the bass bar to the top.
My original fit was actually surprisingly close. It didn't take long to get a very close fit. Things continued to go well, when I mixed the hide glue and got the right proportions on the first try. The clamps needed a couple of thin shims in order to apply enough pressure. I also used another clamp in the middle to ensure consistent pressure.
I suspect that I won't make much progress over the next couple of months, as I have quite a bit of business travel scheduled for January and early February.