Fin selection can be influenced heavily by weighting method selection. I have found that with a 5lb BP, 1 lb STA, weight belt, and some weight in lower tank strap trim pockets, I can trim out nicely with Deep 6 Eddy fins in a dry suit in cold water. But I make a conscious effort to put lead as low on my body as possible.
Keeping weights low in sidemount also allows me to dive in cold water in a drysuit with Eddy fins.
However, even with keeping weights low in weight pouches between my cylinders in a twinset, even with Hollis F1s I have difficulty not being head heavy (yes, yes, I know, when you are as dense as me, it does affect your trim).
I'm still messing around with my CC cold water configuration (I have a 10 lb BP now to reduce the amount of weight in the pouches needed). As I'll be adding a SS stand that will allow me to attach 2 more cylinders potentially, it will move the center of gravity further down, so I may need to stop using my Hollis F1s but instead use Deep 6 Eddy fins (which is what I'm hoping for, as I like my fins to not be black).
I hope this rambling provides some help for the OP.