3 piece Vs envelope?

[Pinballwizzard]

I am preparing to cover my Acrosport II and I get the idea of making an envelope and it seems the competing method is the 3 piece method, a bottom and left and right sides. Just how does this work with the transition from the vertical stab to the turtledeck? I really dread the idea of sewing up an envelope, but I just can't envision how this 3 piece method would work.

 

[bmcj]

 

[acropilotbret]

 

[macwolf]

 

[Neil]

 

[Pinballwizzard]