I've just read the report from the Dornier 228 flight DCALM (possibly the only scientific flight thats been made, the BA and KLM political stunt flying doesn't count) and they had a definite bum sucking up seat cloth moment at 5000 feet 52.75N 002.38E.
We're still currently operating in an information vacuum as to what's really out there.
BD
P.S. I don't intend posting that report up here on a public website as, to quote the author, "I'm sure you'll be aware that this was written for internal use, so is a little rough around the edges, but it seems most appropriate to simply release you the unamended document.
This is regarded as being in the public domain, although given it's not really designed for public consumption so I'd appreciate it if it was kept between aviation or scientific professionals."