It shouldn't tear anything up, as long as you're using them responsibly. I suspect the front of the tractor will get pretty light without some ballast weight on the front. Seems to me the limits you'll find are weight and (possibly) power. A 4' version of each item would fit your tractor better, but that doesn't mean there's anything wrong with the 5'. You'll need to use a low gear using either implement in heavy conditions, but you should be fine.
Here's the "real world" way to judge the strain on your tractor. As your bush hogging or tilling, if your tractor is making constant black smoke, you're overloading it -- and it WILL overheat under a sustained overload. Use a lower gear or take less of a bite. Puffs of black smoke are just fine, but not sustained. Stay in a gear or an RPM that keeps the exhaust colorless, and you should be fine.