Morning Gadge and Shadow,
It's my understanding that all the Reds were a single drive belt from the engine with a rather nasty dog clutch at the cutter deck. But more than happy to be proven wrong if further information comes to hand

Gadge, have a look at the machines in Jace's thread. Both his and the restored red. Because the chassis rails run straight through it follows that the front axle mounting will have a higher pivot point? Is this what you are referring to? It appears to me that the design started with a sensible two rail chassis design with Theo soon realising that the engine sat too high and made the thing look and feel a bit odd. He then sunk the engine down as a production change hence the odd front end/ engine mounting for the rest of the Reds and HDs. I also suspect these very early beasts may not have had the dog clutch and so the cutters were running whenever the engine clutch was engaged. Note this is just a suspicion on my part.
Note the cutter deck mounting detail is slightly different too.
What do you think?