[steam for ever]

Pre65.
Most of the tenders were made with old Gresley coach bogies with tanks filled with concrete.
I have heard of a group trying to recreate one of these and I would like to see this.
I do not know if any different bogies were used but this probaly made them the last big four stock (in part) in service on the network.

For them to be infront of the loco this was most likely for balance but could imporve safety in a crash.

There have been rumours of problems with the tenders.
The most common being the concrete inside will crack and move about which would split the tank and put them off balance.
Cold weather or a strong jolt could cause this.
if this was ever solved I don't know.
Hope that helps you.