Right then, I think I've had a productive day. (Amazing what you can do when you have the right materials)
I drilled two holes in the exhaust housing of the sander:
This was so I could attach the plate I cut and also adjust the height in theory changing the angle.
Ok, so you might not be able to see this but it's around 12˚
I cut the plate pretty much like HB did his. It's not perfect, but neither am I.
Slight issues with vibrating the nuts but not bad for an afternoon bodge.