My choice is 4th hand upwards as a minimum at this vulnerability. I used to play split range, but I now think wide range makes more sense. The chance of a penalty exists, but its hard to get an adequate penalty against an opponent with 55 of anything, even when he is vulnerable. Telling the opponents where your cards are, when they have already bid a major, and you have little chance of taking them to the 5 level, can't be good - as already pointed out.