I have done double vaginal penetration many times - it is simply fantastic. If the woman is aroused enough, there is no problem taking my cock (9.5"x7") and a hung friend at the same time. The friction between the cocks just adds to the general horniness of it all, but the look on the womans face is what gets me going... I've also done triple vaginal penetration at a swinger's party. The way to do it is let the woman straddle the first guy, then let the second guy penetrate her from behind, not kneeling but standing on his feet positioning his cock as high up as possible, then have the third guy insert his cock between the other two guys' cocks. Needless to say it requires the third guy to have a fairly long cock. It's more gymnastics than anything else, and we did it just for the hell of it.