Keep us informed on what you end up with but, I was just going to post how I might approach this but appears Lachau is on it. I think the only "right" way is with the arm and counterweight off. You know the structure the counterweight uses would be substantial, as is the boom mount. However, I doubt (and videos prove) most people will go through that trouble. I am not sure I would sign up to sit in that house and run it while lifting. if that arm rolls, there is nothing to stop it.
If you remove the counterweight, the mass will be forward biased and difficult the calculate based on arm position. But if arm and counter are off, most of the weight is gone, making it an easier lift.
At the very least, I would be looking for a way to lift the front off the boom mount, whether you can mount something there, or whatever. I did look up your machine and does not look like much fun as the weight does not look easily removable.
maybe visit a dealer or two and see if you can get some inside info?