I’d buy some. The LTC3625 a supercap charger chip that does all the balancing work across two supercaps in series. You could put two of your 10F/2.5V supercaps on the board and have a ready to go 5F/5V charger that is plug and play. Alternately, they provide a schematic for a full MPPT circuit for better solar charging.
Or I’d be happy with a board that just breaks out the pins, because it only comes in a “Low Profile 12-lead 3mm × 4mm DFN Package”.
Thanks.