No'3,you should be able to take a TypeVIIC/41 to about 300Ms,it is more agile undewater so is more able to dodge the ashcans and presents a smaller target:hmm:having said that,as you have found out predavolk my friend,when you get to that stage of the war attacking convoys is just near suicidal
you could do a number of things really:hmm:stick to the north atlantic,attack convoys in your nice new deep diving VIIC41,or get a TypeIXC,and use its greater range and go after lone merchants further away(I prefer this option myself,convoys scare the beejesus out of me
)or you could just give yourself up to the allies:rotfl:Whatever you do,I wouldn't advise getting a TypeIXD2,it may be heresy to say that to some,but the thing is just a big huge DD and plane attracter with a dive time not unlike the titanic,with very similar results
the choice is yours!