One thing to remember... the camera only "sees" one side of things.
Sometimes, instead of spending hours posing a scene, so that everything lines up just perfect, it might be better to spend 10 mins and get it perfect from that one camera angle only. Who cares if the penis is clipping the lips on the side not being shown in the render?
Photographers have been taking advantage of perspective and optical illusions for almost 200 years. Why not use the same stuff in DAZ?
I'm not saying always do this of course. For example, you may be making a scene that is very long and involves animations. In that case, the time spent getting everything right first will pay off in the long run, since you can just change cameras and perspective without worry. But if you're just rendering a simple lewd scene, short cuts can make a big difference.
Dicktator is great for this as it comes with all sorts of pose adjustments to move the dick up down, side to side, even curve it in one direction or the other.
Another trick to make that thing "just fit" is to unlock the hidden preferences and then look at the gens at their base level and either use mesh grabber to fudge the one area giving you problems or use the X,Y,Z scale sliders to make the penis or vag bigger or smaller just in the areas you need too. Usually you only have the overall scale slider, but you can unlock all three axis by showing the hidden preferences in your parameters tab.