Frank Neurath wrote...

Has anybody some experiences with flight tests carrying heavy asymmetric
loads in preparation for separation tests?

Yes, but you probably know the drill about public info
and all that. You might try:

Dungan and Clark, "Flight testing large lateral asymmetries
on highly augmented fighter/attack aircraft", AIAA-1994-2138.
It deals with clearing the F/A-18A/D for carriage of a 2000+ lb
guided bomb on the outboard stations, and it's publicly available
through AIAA.

Dave 'gravy train' Hyde