I tried what you described and still have the height problem.
Then i added a new "Krypton Ribbon Form", changed "AllowFormChrome" to "true", nothing else. Startet the testprogramm and still the height changes after minimize/restore.
So sorry, i am not a professionall developer, but i still have the problem and can not fix it.
So it looks for me that i MUST update to 4.1 and check if this still exists there