Got three crawlers myself, but not been out running them for a while. Had them a few years, they were all built in the days before you could buy them off the shelf so I have a
Clod based 2.2, a
Berg based 2.2 and a
Clod based Super which has an 18 inch wheelbase with 7 inch diameter tyres.
Crawling is all about precision and having to work out your own way of traversing obstacles. For fun it's just going out there and trying to work out how to make your own route. If you try competition crawling you will learn what proper precision driving is, as you will have to pass through gates that can be only 16 inches apart.
'Old school' crawlers
http://www.youtube.com/watch?v=0NnToPnQSEw
more up to date competition rigs
http://www.youtube.com/watch?v=bM7C_TJEXYo
and some super class crawlers doing their stuff
http://www.youtube.com/watch?v=ChD2K66flBU
The growing class in crawling are scalers, with the comp crawlers getting away from something scale to something designed purely to crawl.
http://www.youtube.com/watch?v=gT1i-8tfOvY
Speedy Steve showing how capable a scaler can be
http://www.youtube.com/watch?v=yqJh-e0OvqM