i tryed to look at a sim in cvcx for a DD game where i was lowered the penetration as far as the sim would allow. well unfortunately it wouldn't go below 50% pen. it was still profitable by the way.
so but maybe the profitability is a matter of degree when it comes to penetration. or maybe it becomes harder to get as much bang for your buck as penetration decreases. i guess you end up seeing less and less desirable counts and maybe if you do the worse the penetration the more the chances are the hoped for cards are behind the cut card.
here's from the 'good ole book': http://www.blackjackincolor.com/penetration3.htm