Curious, which mod(s) are you using?? Ive just tried this spot in gwx2.1 in aug/sept 1942, all i got was a couple of destroyers patrolling back and forth and 2 coastal merchants, i hung around for 5 days within a 50km radius of your suggested spot but nothing worth sinking turned up.
+ Im in a VIIc with <25% fuel remaining so i think i`ll have hoist a sail if im going to make it back to St. Nazaire without refueling