Nice work Ace, it looks like were getting closer to the final article. I'm sure there was an RN Ikara magazine plan as an attachment on this site long ago, but when the attachments went so did the plan. I've never come across it again on the internet. I would agree with your Perth conclusion since the deck house is pretty wide too.
IIRC, TimothyC had found all attachments (unnamed, unsorted, but the images are there) somewhere..... it might be there still :O
I have some drawings for the escort cruiser and different Ikara equipped never build ships in friedmans. interestingly enough, I think the magazine and loader on the leander seems to be actually smaller then the river class fit.......... and that of hms bristol seems to be the same way, as it in length is limited by the gun position. I wonder about their magazine loads and the size of the fitting room.....