Its a pity you aren't in Adelaide; there is a 8" Skywatcher Dob in the classifieds for $400, pick up only..
I don't really understand why they'd make an 8" truss
They're already a small scope. I think at 8" I'd save my money and get a solid tube.
The main problem I could see with that design (assuming the trusses/struts are rigid) is stopping a shroud from drooping into the light path..