Having sailed on Car Carriers, the last thing you want is a too stable" i.e. "stiff" ship, because it would roll like a pendulum and the cargo would break free. The ideal is a fairly small GM which gives a "lazy Roll" with no big accelerations to stretch the cargo lashings and work them free.
However, in this condition it is essential to watch the "Free Surface Affect" like a Hawk, and the Engineers and Mates have to work together to maintain the list and trim using both Fuel and Ballast Tanks in such a way as to minimise Free Surface Effect.
A further complication is "Wind Induced List", because Car Carriers are very High Sided, any wind on the side causes them to heel, pumping Ballast to correct this, can leave the vessel vulnerable to flopping over in the opposite direction when the relative wind changes. On an old car carrier with an inexperience Mate I used to get called out every half hour all night with a furious tirade that I must have transferred fuel because the List had changed and I must go down the ER to pump Ballast and correct it. The Mate just couldn't understand that every time the relative wind speed / direction changed, the List changed.
I suspect most of the problems are incurring on modern ships with "Auto Heel" tanks, where the Mates and Engineers leave everything to the Automation, and ignore the Free Surface Effect.
The Car Carrier that capsized coming out of Southampton after Bunkering, last year, obviously had a FSE problem, I am not sure if the requirement to reserve Tanks for LSFO had any bearing on this. Practically you are always going to have at least one slack LSFO and one slack HSFO tank.
I was always taught to run fuel tanks empty, and fill them in pairs P&S, when Bunkering, but many Engineers now just open the filling valve to every tank full and let the fuel flow in, leaving every tank slack unless they are taking capacity Bunkers.
Many of the Eastern European Engineers have no knowledge of stability at all.
I had a Polish Second Engineer join my ship with a brand new Chief Engineer's Certificate and a "Degree" from a "Technical University" in Poland. I asked him what he had to do in order to get his qualifications, he told me it was very difficult, he had to dismantle an air compressor and rebuild it!!
No sort of Engineering Exam / training to my mind, just a trade test for a service Mechanic/ Motorman.
It is always better to ask a stupid question than to do a stupid thing.