Was in meeting w/ a head supv for loss mitigation for Wells Fargo about 2 mos. ago. He had range of 80-88% of BPO. The range depended on how much “junk” was on the HUD.
He couldn’t speak for other lenders but this is a good guide. I have a friend that has done some FHA shorts and I believe he said they hold @ 82% of the BPO.
So, as is the case most times, really hammer the BPO and use every tool available to get it as low as possible. Get your own comps, rrepair estimates, etc to justify and make your case.