I'm sorry I do not have a pic of an accurately restored Commando to show you but the parts manual is wrong in it's positioning of the horn. If you are really fussy about the placement you are going to need to be careful, and do a lot of research. Best of luck. Someone on this forum must have a picture, which is historically accurate. Grandpaul? L.A.B.?
Here's an idea. That guy that who bought the last Commando for 30k might be willing to part with it. Sure would save you a lot of time and trouble.