if you have a 26 foot jib boom my advise is rent a larger track machine for a weekend, lots of info about machines nose diving and doubt you can react fast enough to counteract, if you insist doing it get some tractor weights and bolt then to the rear door to add capacity.
with the 743 we have moved concrete barriers 1700 pounds at middle of the forks, even a couple inches off the ground just stopping it liftts the rear wheels