Due to the resistance of the connecting cable, and the resistances introduced for current sensing for overcurrent protection, the voltage at the hub can be anywhere between +4.5 V(loaded) and +5.5 V. This circuit will deliver a stabilized +5 V in both the cases, ie, it is a buck/boost design, using the TPS63000 switch mode regulator chip manufactured by Texas Instruments.
It can deliver +5 V at 500 mA from input voltages as low as 2 Volts so a rechargeable battery and its (USB powered) charger can be added to make this into a USB UPS for the USB hub.
Step 1: Preparing the circuit board
A scrap of single sided paper phenolic copper clad was cut to size and the outline of the chip drawn on its unclad side.
Then with a small screwdriver sharpened into a chisel, material was removed, making a niche for the chip to sit in.
Step 2: Gluing the chip in
This is, strictly speaking, unnecessary but I liked the feel of gouging out the PCB material, and it was fun to add some three dimentionality to the circuit.
Step 3: The ground connections
Since the other side is an unbroken ground plane, this is easy: just drill holes and solder a wire.