I try to put protein in the meals with either chicken,fatfree meat or fish. I still eat salads and fruit, but dont eat any beans
or lentils. As you said one has to experiment, on what to eat.
It's going to be tough, a 5hr journey, but at least there are toilets on the plane, make sure you pad yourself in that area in case of leakage, and take extra padding in case you there is leakage. I guess in cases like ours, we have to try tactics that will or wont work.