Aterpster,
My admonition probably wasn't directed at your good self ...
Chaps,
The limit is a certification matter and has been done to death in previous threads on the subject. One of many is
this one. I note that MFS plays with this stuff day in day out in his day job ....
In addition,
(a) there are certification discontinuities at 20,000 feet
(b) the structural load capability with flaps is reduced compared to clean
in the Standards.
The real killer is that there is no obligation on the OEM to investigate high altitude operation with flaps. Unless the AFM indicates a permission to so operate, a general limitation is prescriptive. Bush lawyering is not useful when interpreting AFM matters.
In many respects there are things which are not explicity proscribed in aviation and this is one of them.
Consider what one's story might be at the Inquiry after the mishap should one have elected to play test pilot with someone else's aeroplane ...
Will be having dinner with MFS in a day or so, so will ask him his thoughts on the matter.