Our old Fahr mowers used to sit like that. Very similar design.
The Unifarm mower we have now has a different backbone design to those, and it lifts up straight instead of flopping. I have NO idea how, just that it does!
I'd be tempted to redrill the top backbone bar at the headstock end and shorten by 20mm, see what it does. If it doesn't work, then you haven't lost anything. And all it should mean is that your linkage will sit lower to get the float pin in the middle of the slot when on the ground.
The Unifarm mower we have now has a different backbone design to those, and it lifts up straight instead of flopping. I have NO idea how, just that it does!
I'd be tempted to redrill the top backbone bar at the headstock end and shorten by 20mm, see what it does. If it doesn't work, then you haven't lost anything. And all it should mean is that your linkage will sit lower to get the float pin in the middle of the slot when on the ground.