The schwinn trailer I got has quick release bolts that mount like a front tire came with 20 " wheels as well...I hauled a mini refrigerator on it the other day (compressor type kenmore)
I'm sure I could mount larger tires but the frame seems plenty sturdy and it trails behind well no weaving.
Low speed is most likely gonna make the whole drive train last longer...azbill keeps his speed way low hauling them 2 little girls around he has racked up some good miles but he does also use the high end EZ motor kit. I imagine in the long run the EZ motor kit would be the most cost effective and reliable from what I have gleaned. I just don't see myself using this as a daily commute once I get a job due to the heavy traffic in the Dallas area but it'd surely get me by till I got a scooter or a car. It looks like the 4 strokers are gonna win out eventually anyhow due to the ban on 2 strokes recently lot of vendors are out of stock already.
Here's a link to a trailer that looks a lot like mine but my box extends back further yet centered on the axles:
AOSOM BICYCLE BIKE CARGO TRAILER CARRIER-YELLOW - eBay (item 120569489141 end time May-16-10 10:36:24 PDT)