Penalties for Pushing/Dragging?

A character can lift as much as double his maximum load off the ground, but he or she can only stagger around with it. While overloaded in this way, the character loses any Dexterity bonus to AC and can move only 5 feet per round (as a full-round action).

A character can generally push or drag along the ground as much as five times his maximum load. (…)

The rules don’t seem to indicate any penalties to pushing/dragging but I assume the penalties for lifting off the ground are implied again?

Also, do you apply Heavy Encumbrance penalties such as the Check Penalty in this case, or is it a separate thing?

EDIT: I’m opening up this question to D&D 3.5 since, after checking, it happens to say exactly the same thing about dragging.

I’d also like to list a few cases to see how people think they should be ruled:

  • Dragging a bag, the weight of which doesn’t put you past your maximum carrying limit. How different from carrying is this? Should the bag be considered 1/5 of the weight, since dragging allows 5 times the normal maximum, and apply regular encumbrance rules?
  • Dragging a bag, the weight of which puts you past your maximum carrying limit but within Lifting Off limit. Is dragging easier?
  • Dragging a bag, the weight of which puts you past Lifting limit but within Push/Drag limit. This is the main case of the question.

I’m going to assume that we’re not in a worst or best case scenario for the above cases, so the ground is not made of ice, there are no wheels, but it’s not friction hell either. The rules seem to imply that, per GM-fiat, slippery ground or wheels would be favorable circumstances and allow dragging even more, while a high-friction ground or object surface would limit further the total weight that can be moved. It would still be interesting to see if you have specific situations in mind that would help or hinder, and how much.