It is a hard call to make some times, especially on hard woods. Cut too far on the undercut and you pinch the saw. Dont cut far enough and it rips.
It was a white oak that nearly got me, a co-dominant stem right at the top where I couldn't get out on it to lighten it up. VERY important to lighten them up as much as possible before you make the cut close to the stem, and then make the final cut as FAST as possible.
After that experience I carry a sacrificial saw (an old Stihl 009 most recently, after the Homey XL bit the dust. Poulan "Wild Things" are good candidates if you find one that runs at a garage sale). If I can't lighten up a heavy branch enough I bury the sacrificial saw in the undercut, just let it pinch. Then I tie it off with 1/4" hemp or parachute cord and make the top cut on the inboard side with the 200t. If the sacrificial saw stays in the cut and the hemp breaks so be it, 'nother homey bites the dust. Better cheap saw than me.
Usually though, if I make the top cut fast enough and close enough to the "sacrificial saw", I get a clean jump cut, the hemp catches the cheap saw, and everything's fine.