Okay so here is the dolly that I made this weekend. It cost me about $50.00 to make. and it can be broken down so it can fit in my Ford Escape while I trailer the boat. Ill post parts list and instructions at some point this week. I used wide tires and used a line to stabilize the extension. It's remarkably stable and lightweight. I've pulled it through the yard and also over some peices of wood and rocks to test what it will be able to do. I think the wider tires should perform well in the sand.