Vertical should be much better. The RF waves are like a donut. The center line is your antenna.

If the antenna was horizontal, the strongest reception would be above and below the antenna and not sideways - the direction in which they best propagate across a room / flat towards the access point.
Cheers!
That means that the stock antenna in the FP Apollo is located in the worst possible orientation and inside a Faraday cage. No wonder it did not work well before I put it outside of the housing!
It 'should' be (famous last words?

) easy enough to make a part to hold it vertical just outside of the housing, and protect against yanking and chafing at the same time.