This is a pretty good question. Most rifles with thin sporter barrels, lacking pillar bedding or even glass bedding, will shoot their tightest groups with moderate fore-end pressure. What they will also often do is change point of impact as the temperature or humidity changes, though. So I generally recommend free floating a barrel - even if it opens up the group a little - and develop a load (if you handload) around the free floated barrel. Stocks with more support around the action (like H.S. Precision) will often shoot tighter groups as well with the barrel free floated.

The main thing to keep in mind, if you are considering removing some stock material for a free float, is to err on the generous side. It doesn't look as good to have a wider gap between the stock and the barrel; but if the stock warps a little on your hunting trip and is suddenly putting pressure on the barrel again - your shot is going to be off if the distance is very far. And when free floating the barrel, it is also a good time to consider glass bedding or pillar bedding the action.