Thanks...But It just hit me; the fact that a VIIC Might be too hard...so I think I might do this:

-Find a fuselage of a Cessna
-Waterproof it
-Hack off the vertical stabilizer and put it under the vertical stabilizers
-Some how move the prop and enging from the front to the back
-Make a wood conning tower
-PVC Periscope!
-Somehow engineer a ballast pump system
-and where the prop was in the front will be my sole torpedo