For vertical take-off and landing, a large amount of available power is needed. Lithium Polymer battery provides this power. Leveraging power and weight, the LiPo battery only need to be sufficient for the take-off or landing operation, not both.
The hydrogen fuel cell will produce more than enough power for forward flight. Excess power produced by the H1 unit will be used to recharge the LiPo battery. LiPo battery will power the vertical descent and landing.
Numbers and calculations shall follow.