Wow, thank-you all again.
As far as someone to talk to, or get lessons from, I would have long since done that if I knew who. No one in my area is familiar with Miniature Horses (and if they are, anyone that I know of is busy breeding less than desirable horses OR using them as cute kids riding ponys in ill fitted tack with oversized riders OR using them as cheap pasture mates for full sized horses and not into driving, especially not properly) and the only folks driving are Amish.
I was told years ago to use bike tires on my cart, before I got out of and back into minis but, duly noted, I will order from one of the suggested places. I do not want any accidents. This is why I am asking, and learning so much!
OK so. We'll see what 20" wheels do for him. I will measure carefully.
I am in the market for two more carts. The one that we bought was from Shipshewana Harness & Supplies. I bought it used at a very good price just to get "something" here to start driving these little guys. I haven't seen any from this company before and I haven't been able to find it online. It is a very solid built little cart. You've all had great suggestions, what brand of cart do you suggest? Again, nothing fancy, just easy entry, is there a website I should be looking on? I have been steering clear of Ebay specials carts. Assuming that is the same as Ebay saddles.
I looked up the harness on Robinson harness, so any of these should make a good pleasure driving harness for these little tykes?
http://robinsonharnesss.com/harnesses/single-driving.htm
I want one with Breeching, so the cart doesn't run the horse over when we stop. I have only driven that one time (at the time the picture was taken so I could ask) because I wasn't liking driving without it.