Thank you, and still working on the posts.
Re: "Btw 5.5 degree up pitch is huge, would cause significant increase in drag, and would not be necessary if the surface below was not rising in the horizon."
At that altitude, drag would be less significant. Decrease in drag based on reduced density of gas. Not enough lift available via designed angle of attack as a result of reduced gas density. Requirement to increase angle of attack.
FYI: Posts/theory aside, I do believe there is a high probability of hollow gas giants existing if conventional system model pans out to be true. Rocky planets unsure, but potentially feasible, potentially layered. In other words, the subject matter is of great interest, but not sold yet that we are on the inside.