I would say as much as posible.

When I tightend the tramp on my H16, I would rig the mainsheet around the sidebars, pull it tight, the curve would bend inwards anywhere from two to three inches. I would lace the line as tight as posible, then release the mainsheet. Boy that tramp was TIGHT!!! I wouldnt even call it a tramp, more like the floor It was pretty tight. So if you see a nice curve you are fine!