Keroberts,
I'd have to recommend against it at present, send them an e-mail and wait a few weeks for a response. With the prime they will probably check back in.
I noticed that you probably checked mikes gap pages since you didn't comment about alexr's.
Things to consider:
The factor density only decreases by about half by doubling the range so ranges around 500-600T are really not that much better than 850T. Especially if you consider they could have sieved and found nothing.
Also if and when you decide to redo I'd strongly erge you to use the 991<n<50M.