David B....that is exactly right! You can go down to an 8 inch tire wheel combination, like I did going from a 15 inch wheel/tire combo. There are some small tires that have relatively light
load carrying capacity.
Did you roll the trailer on just the wheels? That would make the trailer even lower. Could roll the wheel over rubber mats.
Tire/wheel combos come in 4 and 5 bolt patterns. Wal-Mart has some but can be a bit pricy at $42 each. Etrailer!? has them for $24 each but they get you for shipping of $20-25.
I picked up my wheel/tire combos off Craigslist as take offs from a guy who had bought bigger wheel/tire combos for his utility trailer. They were like new but tread really doesn't matter since they will be used so little.
Finally, I have an impact wrench that makes the swap even faster and easier.