if the UK started with about half as many transports, (or even a quarter) but let them carry more that would help.
If convoy raiding let subs try and attack/damage/sink/destroy troop transports that would help. If one could implement that any damage a troop transport suffers, the unit within it suffers as well, convoy raiding would be very helpful.
If you put submarines along the path from malaysia you can starve the UK of precious precious oil and rares. I suspect (but don't know for sure) that hte more subs you have the worse the UK's trade efficiency is, meaning they spend more for the resources they get from the US, or the US can't send as many resources.
If convoy raiding let subs try and attack/damage/sink/destroy troop transports that would help. If one could implement that any damage a troop transport suffers, the unit within it suffers as well, convoy raiding would be very helpful.
If you put submarines along the path from malaysia you can starve the UK of precious precious oil and rares. I suspect (but don't know for sure) that hte more subs you have the worse the UK's trade efficiency is, meaning they spend more for the resources they get from the US, or the US can't send as many resources.