Ok, SH4 U-boat missions is now available through Subsim, which means you get it through Direct2Drive and Subsim gets a couple $$ from the sale--at no extra cost to you.
Click here http://www.subsim.com/radioroom/showthread.php?t=131893
many thanks for your support! You can get it as a download in several places but only this link means the game helps pay the bills.
good hunting!
Neal