I tried to set it up outside to see how well it lays out, but alas the weather was not cooperative. 30 to 40 mph winds are not condusive to setting up a tent roof for the first time, nor are tornado watches and thunderstorms. But here is a pic of the thing folded in half. As you can see it takes up almost my whole kitchen!! I will eventually get one of it set up.
So to start I used flat felled seams throughout. Here is a link explaining these seams. As I was sewing I discovered that my 1 1/2'' seam allowances were a bit to generous, so my finished roof panels are all about an inch bigger than I was planing, but since my walls have the same seam allowance, they will also be a bit bigger. This gives all my tent dimensions a few extra inches.
This next pic is of the welded ring I am using at the interior peaks of my roof. There are three reinforcing straps, which attach to six of the seams, taking the stress off of the seams and fabric.
This is a pic of my exterior edge. You can see the small straps sewn onto the 2" lip. This is where the crow's feet guy lines will attach. The lip has several lines of stitching ran through it all the way around, and sewn into on the interior it are straps which the walls will attach to. The interior and exterior straps line up to prevent sagging. Below that the rain guard will hang down about six inches.
I had noticed when I was attempting to set up the roof outside, that the canvas has a few minor flaws to it. I am not sure if they will be able to be 100% waterproofed by the sealant. So I will be making a simpler roof lining out of some of the huge piles of cotton I was given. There are surviving tents, such as the Carlos V tent, that have a second roof, that hangs a couple inches inside the exterior roof. This could have been to help with the misting that can occur with natural fabrics in wet conditions. I can use the same pattern pieces I have and just eliminate the seam allowances.
Sewing this has given me a very profound admiration for the people who created these tents without the use of machines. Even with the machine, this roof has taken me over 10 hours of just sewing!!! I cannot fathom how long it must have taken to do this by hand.