It *might* be possible to make it with a VIIC to the carribean if you got the larger batteries installed. Though it'd be tediuously boring the moment your batteries get recharged to 100% you go to periscope depth and get 45-90 nm for free (in terms of diesel fuel).
I've had to do this myself on occasion even with a IXC when I get Bfe patrol area down in the carribean or Florida, but along the way keep running into stray targets that are juicy enough to engage (like small unprotected convoys of 2-3 cargo or tankers) so that when I finish my patrol and run out of fish I've been really close to hoisting the sale to get those last 50 miles to Lorient
