It looks like a more recent edition of the super detail Black 5.
I have R2323 '5000'.
I routinely add weight to the locomotives where able, and definitely to the tenders as I don't like them to be featherweight - were half the weight of the locomotive or more in 'real life'.
Recently had mine hauling 12 coaches around my 4th radius circle test track without too much difficulty.
Tender on mine is definitely not that of the old removed motor ringfield chassis.
If this is an issue, I would locate the appropriate Service Sheet and check it out.