My backup plan, if I can't find a long RCA jack, is to mount them to an aluminum panel under the thick plate as you said and bore a large hole in the thick plate. I wish I could do it the other way because it would look sooo much cleaner but you can't have cake and eat it, too.
Your comment about not drilling large enough holes (like on the Bryston) was actually a concern of mine. While my ICs now have RCA ends that are slightly less than 1/2", I don't know what my future ICs might have. What ICs did you find too big for the Bryston? I was thinking of boring a 9/16 hole but I'll step it up if there are a lot of ICs out there that have ends over 1/2".
Your comment about not drilling large enough holes (like on the Bryston) was actually a concern of mine. While my ICs now have RCA ends that are slightly less than 1/2", I don't know what my future ICs might have. What ICs did you find too big for the Bryston? I was thinking of boring a 9/16 hole but I'll step it up if there are a lot of ICs out there that have ends over 1/2".