Hollow Earth

I'm willing to consider that planets might be hollow. The smaller asteroids, comets and very small moons could be hollow, but likely are not, unless someone hollowed them out. With larger bodies strength of materials is the problem. No known materials are strong enough, not even the optimistic projections for CNT = carbon nano tubes. The interior of a hollow Earth could be filled with hydrogen or other gas at about a billion pounds per square inch. That would support the weight of the very fragile crust in a very critical balance. How could extreme pressure hydrogen get there? Why would it not leak out? What sort of creatures could live under such extreme pressure? The mass of the gas would exceed that of the crust. That would not be hollow by usual definitions.
Some claim there is no gravity inside a hollow sphere. I think that is wrong. There would be perhaps 1/10 th g at the inner surface, decreasing rapidly to near zero in a few miles, depending somewhat on the wall thickness= crust and the gas pressure of the interior atmosphere.
A center "sun" would require station keeping and very low mass, otherwise down would be toward the center, not toward the inner surface. The "sun" could consist of a large array of very high efficiency, narrow beam, artificial grow lights aimed at the spots where agriculture was performed. The rest of the inner surface would have about the light level of a moonless night = starlight. Nearly all the light from such a "sun" would become low grade heat, in less than one second even if most of the inner surface had the highest known reflectivity that modern science can achieve. That would make the interior extremely hot without a means of venting huge amounts of heat energy to outer space.
It is difficult to explain how any of these models would explain the behavior of seismic waves, which we have studied extensively. The source of Earth's magnetic field would also be difficult to explain with any of these models. Please embellish, refute or comment. Neil