What is the favorite size for a twin engine model?
I really don't want to jump all of the way to a 36 but if the other lengths have handling issues.
Thinking I might have to start looking for a bigger one and duplicate my 598.

No handling issues with a 28 or 30 that I have experienced or read. I have a 30 but the 28 and 30 look the same to me when I see them on a trailer or on the lake. They are only 300lbs between them and less than 1 1/2' in length.
Lot a big HP 28's and 30's out there. Seem pretty bullet proof with twins and much easier to have a reliable 100 + boat. My buddy has an older 28 with 496 HO's, stock Bravos and runs mid 90's. I am running 525efi's which seems to be the lowest power anyone puts in a 30. I am more than happy with this power level but everyone else near me has SC motors or Ilmors.
I have added an extension box, then shorties, then 5 blades. Handling is the same at each step but definitely faster with extension and shorties.
I lost a drive earlier in the summer (ate an upper gear set) and the only thing I noticed was that I was losing speed and the motor was bouncing off the rev limiter, it was running straight as an arrow on one drive.
Having said all that, it is not a rough water boat IMO. I would like to ride in a 33' and see what that extra length and weight feels like. Doesn't seem to be many 33's around.
There is one 36 on my lake and much different design than the 28/30/33.
30' is the biggest that fits my dock and I can tow with a gasoline F150 so that is my limit.

Nice 30' in Wisconsin ...