All the comments about the limits of the lathe are absolutely valid and I fully agree with them. However, it should be pointed out that there are situations that require off-centre turning, which can result in unbalanced work. The biggest issue for the OP here will be the inability to reduce speed below 500rpm (which is way too high for a large unbalanced piece, even on a much bigger lathe).
I think the way to go here really is with the advice to have a separate disc behind the chuck with counterweights mounted onto it.
Hi Fuzzyturns, Thanks for the endorsement of my suggestion about actually counterbalancing the work. It won't address every situation but it's a relatively simple solution and removes a lot of stress from both the lathe and the turner.
