1.   Wings, fins, cockpit removed and filled.  Inverted.  Conning tower, deck, props and such added.   1/72 Hasegawa kit becomes a 1/700 scale submarine
2.   Cloth wings, vertical fin at 85% final size.   Propellors have two blades.  
3.   Twin vertical tails keeping the D.H. family shape
4.   Butterfly tail using horizontal stabilizers with approximately a 1/2 inch long plug added for 1/48 scale versions.
Paint schemes decided at one's leisure.