Jim..I top feed. The worms are surface feeders and so by feeding the surface, there is room for more to "belly up to the bar". It also helps in not heating up the bin or causing it to go sour.
The worms will reproduce to the space and food available to them. Get a bigger bin and more food..get more worms!

Top feeding will also get you lots of flies and some smell as it is not buried with the browns making for the right balance, but too much food and you get too much heat and possible anarobic conditions but even then most people who have been at this for a while will tell you that the worms will congregate in these areas also. Don't forget to put in some crushed eggshells at least once(and it doesn't matter how much).

When I top feed there is always a good 3" layer of shredded paper on top. There are no houseflies and no smell.