If I want to make a custom portrait for use in IWDII, what sizes do they need to be?

Same as BG I&II and IWD I.

Small: 38x60 and large: 110x170.

That's incorrect, the dimensions for IWD2 are completely different. It's 210x330 and 42x42 if the pack I've checked has the correct sizes (I don't have the game installed so I can't check, but it should be in the readme).

Hmm? The ones I've downloaded have been the same size as the other IE game portraits.

EDIT: But... The readme says what Tal said.

I used a 110x170 in IWDII and there was black space, it was too small. 38x60 fitting ok though.

thanks Tal.

It says in the readme file, correct sizes, just check with that.