Not impossible, but requires practice, patience, and probably a partner that has been able to deep throat a good-sized cock in the past.
I've always been able to deep throat, and can take 8x6 all the way to the base. Have also managed the same with a bit longer or thicker, but not both, and I've had to work up to it.
Early on, an important factor for me is that we are both working it in. I can make it slick, prefer a heavy pre-cummer for that extra smooth glide, and open up for him, but his feeding it to me in a slow, but steady manner as I adjust really helps makes it possible.
That's my experience, though. Hope
FleshlightMouth, who is like the deep throat master, chimes in on the thread. :notworthy: