Trying to do it any way is sometimes a bad idea for tortoises. Sometimes the male will be flipped onto its shell while otherwise engaged.
Not sure if I would consider Bonobos as quadrupeds, they do walk on the knuckles of their front hands, but they will sometimes mate face to face.
Also, are you aware that the female breast developed larger than those in other species to give the male something to do with his hands while mating in the missionary position?