Phil,

try the following formers for the T10. Scale up for the T20.

They are already adjusted for the additional size required. Parts are on a piece of letter sized paper. Print PDF at 1:1 evidently.

By the way, I found the system for F3 to be a real pain when building the fuse. I'd just cut it out of a single piece of 1/8" lite ply. For the FW, I'd use 1/8" regular ply. I also sized the inner hole in the firewall and spinner ring so that a 28 mm can motor can be slid in from either side. A cooling inlet will be needed on the underside or two little NACA inlets could be made on the side - perhaps cooler looking.

The dashed line in F-3 can be used for a former doubler (say in the T20 or T40) or one can simply use 1/2" lite-ply rings around the dowel holes as shown for the T10. Oval holes in the FW as shown in the second pic might allow a little more airflow over the battery and ESC.

Hope this helps.

David.