A thing of beauty Norm!
I now understand that there is a front mounted deck point as well! My incoherent comments on the weekend did not account for this.
I've discovered some photos of a stallion (from the nineties I guess an so later than yours) that has a more conventional height adjust. Seems old Theo got it right in the end.
The thing I did notice on the Stallion photos is that his has slotted holes and the usual Anti-scalping wheels to allow for deck float. I'd send photos but I'm finding it a little frustrating at the moment. Refer query in seperate post.
Again, full marks for the ingenuity!
Cheers,