Tony, thanks for your reply...
I'm willing to bet that if you were to weigh your truck with and without that cap, you would find it goes a bit over that 200 pounds.. LOL Most likely, it's in the 350 pound range, unless this is for a small short box truck.
In any case, do not plan to mount any sort of eye bolts through the roof, attached to any sort of roof rack that is on the cap already or into the mounting rails, be they aluminum or what look like a thick fiberglass... The latter are actually wood boards that are encased in fiberglass, the wood usually being a cheap grade of pine.
Some have tried to come up with a C type bracket that 'clipped' onto the inside cap mounting rail, but extended to the outside of the cap with eye bolts in them.. Sounds great but the issue was the twisting strain to the inside rail of the cap was too much and ripped them off.. Not a good thing and NOT covered by the warranty for some reason either.. LOL
From my experience, your safest bet will be to use a pair of angles, box rails or even 2x4's that have some sort of clamp (cap clamps, C clamps etc..) that will allow you to clamp the angles to the mounting rails to keep them from shifting. Make them at least 4" longer than the cap is wide, and attach your eye bolts/cables to them. This will help protect the outside finish of your cap, and keep the lifting rails in place, as well as help keep the cap from spreading too wide in the back door area - which is a very weak area to start with.
The other thing that most have done is to either add a steel 'H' frame rack that goes above your cap to keep all 4 cables in a vertical position to help keep the cap more stable and also keep the cables off the outside finish. Or, they have used 4 separate pulleys mounted to the rafters for the same reason. Once set up, the 4 cables can be attached to a single cable with a 'D' ring which will allow you to use something like a boat winch or such for the actual lifting..
If your going to try and use one cable to support your cap (say from the steel 'H' frame rack mentioned above), be sure you make the balance point forward of center as the front of the cap is heavier than the back (assuming you have an aluminum back door).. If you have a fiberglass back door, the back end will most likely be heavier and require the single cable be to the rear of center..
A fiberglass cap can be lifted from the inside roof, as long as the weight is equally distributed throughout the entire inside roof area.. but that type of lift works well when there is a lot of floor space to deal with.. which is not your case as you mentioned.
I hope this helps some...
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