I don't think you'd connect the center tap to a humdinger- you'd connect the center leg of the humdinger to ground (or even somewhere about ground, floating positive) and connect the outer lugs of the humdinger to the filament leads- 12.6vac in this case.
I don't fully understand what they intended with the 70v taps on the Antek PT's. If you're using the PT with a bridge rectifier which is the most efficient use of the windings the 70 volt tap is referenced to ground one moment and B+ the next. If you use the PT with a full wave center tapped arrangement you won't get as much current out of it but you could use the other taps as intended.
What kind of output valves are you using?
For KT88's or 6550's I'd use the full winding (470 volts) and bridge rectify the whole thing for around 650 volts. I'd add a winding for bias (easily done with a toroid) and if needed use an additional tube or a mosfet for a screen voltage regulator with the gate fed by a voltage divider so that screen voltage tracks plate voltage. It should allow maximum power from big bottles.
With 6L6's I'd probably connect the PT using a FWCT arrangement with the 400v taps. It isn't the best use of the antek PT and the voltage is on the high side but it should be OK.