I have had the Hornby 8f's pull 40 wagons with ease the black 5's can only manage about 7 Bachmann mk1's
The most i got with the Bachmann mogul's are about 5 mk1's and the Hornby brits the most they can cope with is 12 mk1's
I have not added weight in any loco they are as they are when they come out of the box.
The track I use is code 75 I have been happy with how they run
mark