Learned a lot - Chieftains, at night, IMC (down to minimas) full payload, minimum fuel….that sorts the men from the boys.
I found the Navajo/Chieftain pretty easy in IMC, and yes, many Bass Strait crossings, have they made them harder to fly, or are you saying you are flying it overweight or with less than favorable maintenance. I'm not sure why some seem to think the PA31 is some sort of beast, it's pretty simple and easy if you just follow the POH and don't get slow, and with RNPs everywhere now you don't even have to circle at 300ft at night anymore (yes you could do that a while back). Granted a 1.5 hour endorsement is a bit lite on, and that should really be in question, not whether you need to do hours of ICUS. PS it's the asymmetric stuff that will kill you in a light twin, unless you get regular practice at it and load the aircraft to perform on one engine it will catch you out eventually. If you can't do an approach or operate in IMC safely in a PA31, you'll probably kill yourself in something else anyway doing the same.