I'd say a bit flatter than 12"!

Had a grain tipper with low "V" bows - that is the bows were straight from the edge to the point then down to the other side. Tarp was crap so I re did the whole set up.

Local steel fab place bent 25mm square into curved bows for me.

Reckon they have about 10 inches raise to the centre of the 8 ft bin.

Too much slope. !!

When the tarp is wound back to rolled position, the roller slides the last foot or so on the winding handle end. Less slope would still be enough to clamp down taught and water tight without causing this [minor] problem.

I'm used to it, but anyone else who rolls back my tarp gets it messed up!