How do you feel about giving these girls oral,have you found it off putting,their hygiene?have a big size girl face sit you?Personaly I only have a bj from them.A size 16 ,overweight,tend to put me off in general.
Why do you ask about hygiene? In my experience, its no more or less an issue than anyone else.
What can be an issue is how much fat they have around the vulva, it can need two hands to part it enough to get to the clit, and then you can't finger them at the same time. But that can also be an issue with smaller ladies who happen to put it on down there.
Face sitting with them facing the bed-head, I'd be worried about because its harder to get to grips with the problem.
I like 69 but I have a belly and if a lass has one too it can be hard to get aligned. Other than that, don't sweat it. And if your tongue won't reach, get creative with fingers.
Size 16 is hardly big, in the grand scheme of things.