Back to the dozer thing; an 8 ton dozer like the previously mention Deere 450g has about an 8' blade. That is about 1 ton of machine weight/pushing force (generally about the same in my experience) per foot of blade width. To get comparable dirt worker performance, I'd think you'd want about the same weight per width; or about a 3" blade on a 1/4 ton machine? so basically I am saying a 3' blade on a 500lbs dozer would probably be about 1/12th as effective at working dirt as would be about the minimum professionally built and designed machine. I am not sure if that is exactly how it works, but I suspect it is close. The 1.5 ton CUT with a FEL and 5' bucket I grew up with can't push dirt to save its life. It gets the bucket under the dirt and then has to lift it out. Basically, what it boils down to; If you want a crawler from a lawn tractor, don't put a blade on it. Put a bucket on it if you want any hope of making a useful dirt moving implement.