A: You will need to allow a few inches of additional bar width in addition to the width of the backdrop to account for fabric variations when rolling up, which happens if the fabric is not mounted precisely level or if the fabric has any stretch to it. With that said, you would need the 98" pole, but we can cut it down to 90", which would be the recommended amount of excess pole.
Regarding the chain length, you should order enough for the longest backdrop you plan to mount on the system, and it will only revolve to the chain connection point. Having an excess chain is not an issue, it will just hang down a bit more.
I hope this helps. Feel free to call us during normal business hours if you have additional questions you would like to discuss, as this is a custom order, and would be non-returnable.