Well, most kit manufacturers did not include the top view to discourage scratch building. Sterling was very good at this. My Minnie Mambo, which is taken from an original kit has the firewall 2 inches wide. F1 is 2-3/8 and F2 which is directly behind the wing is 2-1/8 wide. The rest of the formers are positioned for a straight taper back. All are inside dimensions of fuselage. The critical point is the horizontal stab position in relationship to the wing saddle. Make sure this is held or you will have a wild Mambo!! My current Minnie Mambo has an ACE single channel pulser with a OK Cub .049. About 200 flights to date!! Here is a picture of the finished fuselage less the wingsheild block from the manual. You can see the straight taper.

Bob Harris