Just for reference, I've never seen that strap between the top shocks for the 'S' type rear mudguard on any other bike than mine. All the one's I've seen have all been later dates than mine (Apr 69) and have the mounting bracket off the web and the mudguard has a different shape and different holes to it like my pictures in the rear mudguard thread. I know this has nothing to do with F/B panels, but I just had to say it and I don't doubt that mine was that way from the factory, it all fit together just fine including the holes for the guard. Also the part numbers for that strap and rear guard seem to be non existent for mine. That strap also makes for hard mounting of the dog leg bracket for the 'S' pipes with that special 'stud' that mounts the shock tops and the seat knob. If anyone has seen that strap and mudguard like mine, I'd like to know about it but it's probably before Apr 69.
Also, I think the original F/B (first Commando) had a completely different arrangement for the mounting of the rear fairing and guard which is pretty much listed in the 68 Spares List. Not sure about the later F/B, I guess that's in the supplement.
I think the F/B is the best looking of all the Commandos, but I like the ones with the peashooters best instead of the 68 cigars.