I have CaCl-filled tires (adds about 800lbs on rear axle) and 420 lbs of wheel weights (also on rear axle). I usually have some type of implement on the 3pt (at least 550lbs) which is about = 700 lbs on the rear axle.... all told I have around 1900lbs of counterweight on my rear axle. I can lift full loads in my grapple bucket and go pretty much anywhere without feeling like my rear end is lifting, at least not too much. The tractor *feels* good, certainly much better than with no wheel weights or implements (then it definitely *does* lift the ****-end up with a full FEL).
Note that I blew a front end twice using only the CaCl tires, so they're definitely not enough.... .... now I don't use the FEL for heavy work unless I have some implement on the back + the wheel weights.
My backhoe weighs in at 1400 lbs, which means when it is connected, my counterweight is 1400x1.2 + 800 + 420 = 2900 lbs on the rear wheels. Big difference. No problem whatsoever with a full FEL.
In my view, the boomer is too lightweight in the rear with a FEL attached... you definitely need serious counterweights IF you intend to get your money's worth out of the FEL. If you're lifting dry wood shavings all day, you'll be fine. Not so for wet soil.
You can also reverse your rear wheels (dish out) for a wider track and a little more side-to-side stability.
In the end your stability is 100% up to your skill and common sense as the operator. Don't do tight figure-8s at top speed on a 45 degree incline unless you want to seriously test out your ROPS.
