You know, I’m kind of surprised that Larry didn’t include US Submarines in costing 3 IPCs for convoy raiding. Historically, the US submarine force did the same thing to Japanese merchant shipping that German U-boats did to Allied shipping in the Atlantic. In fact, the US submarines were actually successful at it whereas through convoying and ASW improvements, the U-boat threat in the Atlantic was gradually reduced. US subs were so successful that in 1944 the US Navy had to cut back on submarine production because they already had too many and were running out of targets since they had so crippled the Japanese importing.