Help with a Hydroseeder!

I have a 400 gallon hydroseeder that I would like to make larger, say to 800-1000 gallons. It has a mechanical agitator (paddle) in the belly of the tank, so that is a consideration because I don't want to damage how it functions. Has anybody done this before? What should I be careful of? It is just so expensive to buy a larger unit, and it would cost a lot less to cut the tank and weld on another section of tank, as long as I do it right!
Anybody in Eastern MA know of some good welding people who could do this?

 

Seems your talking a lot of money here, bigger motor, larger tank that needs to be made to the same size and shape, extend the paddles.......
A nurse tank might make better sence, if you think it will work for your set up.

 

The nurse tank makes a bunch of sense. It's no real big deal to make the tank bigger, but why bother? I've only got a 200 gallon seeder, but I carry a 1,000 gallon nurse tank on the truck. With a litle creative plumbing I have it rigged so I can leave it hooked up and take the whole seeder trailer with me to the closest pond where I can draft water, or I can unhook the trailer and draft with a seperate pump. I use a jet agitated seeder (which I built myself) and set the pump on that up to draft and fill either the seeder tank or the nurse tank, then swap one hose and draft off the nurse tank. Working alone I can seed about 4-5,000 ft per hour with this setup. Maybe not the greatest, but it works for me.