After modeling the basic shape of the horseshoe I divided
it into 6 pieces, and made patterns of these.

I printed them fullsize and glued the print on cardboard.
I folded the cardboard tank together and test-
fitted it on the bike.

 
 

All fit well, except the clutch cable was rubbing so I modified the patterns a bit.
Now I need to figure out the mounting and oilline connections and then make
the whole thing in steel. To be continued...