Just a few penneth on the subject...
A friend of mine (for past ~15 years) {well, acquaintance, as she's in the USA and although I've been over there a number of times, we didn't get to meet - she's near Boston and my trips have taken me to Chicago, San Francisco and other places in California}
Anyway, she 'has a thing' about older men, which fits me (next time she gets to Europe, perhaps, unless she is married by then) and we discussed everything under the sun, sometimes online, mostly on the phone, in calls lasting 2 or 3 hours at a time (at 1p/minute it was hotter than any 0898 call, I can tell you).
One day she was asking advice on ideas for positions, explaining she had (at age 32) still not had 'plain vanilla' - ie from age 17/18 she only ever indulged in anal sex.
It doesn't especially appeal to me, and I asked all sorts of questions, but as someone pointed out earlier, with a condom, plenty of lube, and in the right mood, it is easily accomplished, and there should be no pain.
As she put it, what comes out can be of similar proportions to a man going in... She was actually wanting to get some suggestions for a position which she could use as her 'then' fuck buddy was 6'8" and had very long legs, so if she laid on the edge of the bed, he was too high for comfort. (I think it was either that he'd be bent, or could not take her weight and he was too tall for her knees to go over his shoulders.)
I suggested a few pillows, with a towel and then cotton sheet over the top, so she'd get no friction burns. I think he had a couple of cushions on the floor, to help get the height just right, and so his knees were comfy too. So he could build up to giving her a thorough pounding while she used a vibrating egg to ensure her enjoyment.
Seemed to do the trick as she discussed the outcome with me a week later