Astonishing, hey?
Never saw a convoy with five total merchants and all five were the same type, so that's a first.
Back to basics, forget generic and use the actual ships;
1X Large Modern Tanker 100%
1X Large Modern Tanker 75%
1X Large Modern Tanker 50%
1X Large Modern Tanker 50%
1X Medium Old Tanker 100%
1X Medium Old Tanker 50%
1X Subchaser 75%
1X Fubuki Destroyer 40%
1X Minekaze Destroyer 50%
Most of the accounts I read the convoys were small, and whatever size they were there were few escorts, most common was 2 to 4 ships with one or two escorts. So that seems to be working okay so far.