Slightly drifting off subject: aplogogies, but prompted by your statement about using 'wet' for takeoff as standard. In the 80's I used to work for an airline that followed your policy. However, I now work with one where we are supposed to calculate dry & wet, when dry, and use the more limiting. The reason being that wet, due to the lower screen height of 15', could give a higher MTOW than dry. I suspect that when dry most crews just go with that. Time is too tight to do double work. Thus I do not know when, or how often, wet would give a higher figure. I suspect it would only be so on long rwys where the lower screen height is useable. On short rwys I suspect the stop case will reduce the wet MTOW. Thus, it would seem, that to say wet MTOW will always be lower than dry and therefore give a buffer is not true.