well if it was me i would make it little hight and put some seatbelt mounts on there a cage should really protect you, lol
just jokeing looks very cool how are you planing to mount it? right to the roof sheat metel ?
i have roof rack mounts that the PO put on just bolted throught the roof sandwiched on a piece of rubber. works ok have held alot of weight.
If i were to have done it i would have lined it up on the cross members to give it extra rigedity