Cosmo,
I can think of one example where I would have no problem climbing to FL390 with max FL384 (or lower) show... It's in the post that I linked to.
Do you have a procedure to modify the cruise CG? We don't unfortunately, but when it is changed from the default 15% to probably a much more realistic 19-22% the max alt 'magically' increases significantly
Sorry about this, but from that other thread:
...I select CON when I need to. And I do so routinely due to the way I operate the aircraft...In fact, I always select CON with a <15 knots window.
However, I do not set CON routinely, only when I suspect it might actually be needed inline with the FCTM and the recent Bulletin. I don't see any specific issues with CON mind, just CRZ is the intended thrust limit for cruise and I prefer to operate these strategies with specific criteria in mind rather than get into a routine that is, strictly speaking, a deviation - however trivial or slight (or non-existent in impact) that deviation may be.