Mike, and here is the guy you sold the extra three wheels to! I can't believe you told me about this site! I've done nothing but read on here since you and I met. This has got to be one of my favorite sites now.
I did a bunch of measurements the other day when I got home and you will need spacers for the Rubi wheels to clear aftermarket hubs. I have used "adaptit" spacers in the past and they are good products. They are made here in the USA. Here is the link for the ones that I'm going with. I would say that each individual should do their own calculations just in case there are any differences between aftermarket hubs. They are actually adapters as I already have hubs that I am going to use and I am going to make my own axle for my scratch built trailer. My hubs are typical 5 on 4-1/2 bolt pattern that I will adapt to fit the Rubi wheels which are 5 on 5 inch bolt pattern. I will need a spacer that is 1-3/4 inches thick. Since the trailer will not be very heavy and for what it will be used for I think the adapters will work fine.
The best way to find out exactly what axle you need is to get your wheel/tire combination together first. Set them under or beside your trailer and adjust where you want them to fit and get the look you are after. Before special ordering axles, which could get expensive, check out Northern Tool as they have a variety of axles and you may get lucky. I have used their axles for years. You can also get "dropped", straight, overslung, or underslung to help you get the balance between the trailer and Jeep as far as height. The main thing is to maintain a level ride.
The thread for my build will come when I get all of the parts together. I hope to have mine done by late summer of 2014 as I have a big trip planned for the OBX of NC and I want to take it with me.
Good luck on your build. I'll be watching. If you decide to go a different route on the wheels I call dibs on your Rubi wheels!
Thanks again for telling me about this site!
Link for spacers/adapters
http://adaptitusa.com/5x450to5x500wheeladapter.aspx