No need to overfill....you'll recall that tank 11 sits higher than all the others. So CG remains roughly constant until tanks 1-10 are full, then it starts to run aft as tank 11 continues to fill. So PTOBO vs PTOTR is a function of ZFCG and total fuel load.
We would sometimes encourage the loading of the aft hold in order to achieve a 54% take-off if heavy for its (small) fuel burn and performance benefits. Careful ZFCG management would minimise the Burn/txfr..
There was always more to the operation of this aircraft than first appearance suggested!