I think that you will get several answers to this, however these would be my thoughts if they are any help.

On the issue of load height. :-

when you have forks only or are handling a pallet it is easy to judge 4/6". When handling paper rolls with a clamp it is difficult for operators to judge where the bottom of the load is. It is just not visible and certainly the operators are not going to pick the roll at the same height every time therefore it is necessary to give more leeway. I think 12" is about right.

On the issue of traveling in reverse, I think that depends on the size of the roll. If visibility is compromised then you travel in reverse and look in the direction of travel. otherwise you travel normally. For me damage should only be an issue if the operator cannot see what he is doing. it is not really a question of forwards or reverse.