The hardest part about making a cage that is the same shape as the bows is getting the radius of the tubing to match the radius of the bows as it curves over the truck. You cannot bend tubing that is thick enough to act as support in a rollover at the same radius as the thinner diameter bows without kinking the tube. My thoughts were to do exactly as the OP did, but to then add a thinner bar that maches the radius of the bows to outside bend. This would take up any slack in the top and when the top is off, these could act as a handle to climb up on to the truck or as a tie down point.
Here is a crude picture of what I am talking about.
Here is a crude picture of what I am talking about.
