Mr. Matt, according to Honey Bee Democracy by Thomas D. Seeley a test hive provided some answers to your questions. Honey bees carry off trash accumulated on the bottom board. In the real test, wood shavings were placed on the bottom of a hive intended to attract swarms. The hive did indeed catch a swarm and to the surprise to Dr. Seeley, every little bit of sawdust and wood shaving was removed from the bottom of the hive with a top entrance.
Dr. Seeley was attempting to determine what swarms prefer regarding: top entrance, bottom entrance, various size entrance holes, size of the hive etc. This test was on an island that offered a control basis due to isolation as bees will not cross large bodies of water.
For your question on top entrance and adding supers; place the entrance as you please, then leave the entrance in place. Simply stated place new supers on top of the entrance and don?t keep moving the entrance as you add supers. Just my advice, no data to back this up, just my experience. Honeybees are sensitive about their entrance: I can remove a top and look inside a hive with little bother to the bees. However if I mess with the entrance the bees get riled very quick.
Blessings
Van