There is an article in an old Hornby Mag (date to follow) this in conjunction with Silver Sideliles post sorts this loco out. You can get a bit more weight in the 14xx too. A lead idisc in the smoke box plus a bit in the fire box top, Tny bits of "golf " tape in the boiler sides and on the tank sides can add 15-20 grammes, Every 4g is an extra wagon and every 16g a coach! However a 14xx is a couple of coaches max load,