I can say with a bit of certainty that I likely weigh about the same or more than most of my mates. Not by a lot, but I dig on skinny/lean men, and I am considered an athletic/thicker/curvy/voluptuous woman aka I got some tits and ass.
I can't think of any position that I haven't accomplished...even in the last month...
except for being a 'spinner' (in asian countries, little [sized] girls are placed in baskets suspended from the ceiling, sitting cross-legged [indian style] and there's a hole cut in the bottom of the basket about where their vagina would be, and men lay on the floor and the asian vagina basket is lowered onto their trouser snakes and then the asian vagina basket is spun around in a circle, and the purple headed yogurt slinger that slings it's yogurt last, is the winner.)
please don't ask me how I know that....
anyhoo, sans basket and the whole asian thing, a man would pick up his little lady and 'spin' her around on his cock, persay.
Yep, I can't do that. I don't really think I'm missing out on much, though, considering I regularly can do the following:
missionary
cowgirl
reverse cowgirl
piledriver
scissor
the flying V (I sit on counter top with my legs up in the air like a 'V' and he holds my legs up, below the knees, and goes to town)
rocking horse
the X (also a total favourite)
the ape (god damn this is so hot, I love it)
him sitting on a chair, and me straddling him (a shorter chair works best where my feet can hit the floor)
tippy canoe (him laying on his back with legs together, and I come sit on him, kinda squat like, but with both legs on either side of his hips)
indian style (him sitting cross-legged, with me sitting on him with my legs wrapped around his waist)
anyways, I could go on...but you get the point.
Hell, to think of it...
it's really not the size of the girl you should be worried about with all these positions, it's the size of your penis.
if you're hung like a tuna can or a field mouse, I doubt many of these positions will be working out in anybody's good favor...no matter how big or small she is.