Below is a page from the 26 U manual. It has the hoist foot and suggested leach. From these numbers you hold the “foot” square to the hoist or mast and then the actual foot is a line from the bottom of the hoist(luff) to the bottom of the leach.
leach girth (also square to the hoist/luff) will give you the roach. Drawings always have a nice curve but between battens it should be a straight line.
I have measured 4 sails and they are all different. Close but different. Botts has a larger roach. Old sails are stretched and are larger. My new sail, North, made in Sri Lanka, is heavy, stiff, but has a really nice shape and is powerful. At first I wasn’t sure but it works well and reefs well, and I am very happy with it.
Also the weight varies. Heaviest sail with slides and battens (North) comes to 64 pounds. Lightest is 45. The cloth you choose is as big a deal as the cut. Then you must choose standard battens, full length battens, or only one full length top batten.
Warning! 
The numbers for the reef points look like they are right but they are labeled wrong! CLEW should be TACK and TACK should be CLEW. Now, most sailmakers would catch this error but if they just blindly go forward you might have some issues later.
I took these numbers and put them into CAD. Also, background is a drawing from the manual and way in back is John Newel’s gaff rig for comparison.
26 Sailplan from Owners Manual.pdf (31.9 KB)
Or a share link may work for you, CAD here Onshape
Tom
26 C # 28 North Star
Penetang