Aimee needs help designing a steampunk Airship. Any takers? (Roland?)

For story reasons too complicated to get into here, I'd like to have most or all of the living quarters down in a gondola suspended below the balloon. So more like the semirigid or nonrigid airships in the diagram above, although I'm not actually set on it not having a rigid frame.

The Hindenburg had capacity for 72 passengers and 40 Crew Members. It was 250 meters long and 40 meters in diameter and used hydrogen gas to stay afloat.

I'm thinking of using hydrogen gas in my story too despite (or perhaps because of) the fire potential. How big do you think my airship would have to be to need about 8 to 15 crew members while having capacity for about 15 passengers (hotel-like setting, not just seats) with an equal-sized cargo space?

I'd like to create the hydrogen in situ using Chlamydomonas reinhardtii algae, similar to Vincent Callebaut's dream, but built like a ship rather than a city. What kind of lightweight medium would you grow algae on in an airship setup?

Here are a couple of other diagrams that floated my boat. (Click on any image to find the source of the pretty pictures.) Now I'm ready for your ideas --- go!