How long of a lever are you using for a handle? I can remember one of these in a welding shop. When something got cut, one guy was on the handle, the second was on the floor aligning the piece, then both would haul on the handle. On a long plank, six foot or so, you may get more pressure.
I've got a little over 4' of 1-1/4" schedule 40 steel pipe, and another 4' of 1" pipe that slides inside it, so I can extend it out to about 7'.
I'm thinking about making an extendable "plank" using the same technique basically... Mounting a steel pipe on the underside of my cart, with another one that has a foot on it to extend out the back. But this all kind of hinges on if I can make it do what I want with even small stuff...
I don't have a second person, so I've got to be able to set it up, and cut accurately by myself. I've got ideas for a relatively simple clamp I can make to hold pieces where I want them... I dunno, I'm going to have to do a little more learning on this I think, and maybe some experimenting...