The problem with tit fucking is the physics of the tits, they are rather tight and springy, so they don't sag way down, but that make them resistant to wrapping around the players cock. Monica naturally, Saiko doesn't have enough rack to give it a shot. They'd have to figure a way to soften/deform the center of the cleavage, but leave the rest of the tit as is, then she could hold them together and you could get something happening. Till then, titfucking just isn't going to work.