Just watched it. The price of files is cheap compared to lost production, get it done and get back to cutting.
When falling the chaired tree, it's important to note the force the falled tree is placing on the remaining trunk and the intergrity of the connection point. You may push on that trunk and have the broken piece come straight down while the trunk goes over, putting you in the strike zone.
Many chaired woods trees have a certain amount of force pushing straight back, especially if the top is jammed up against another tree, stump, etc.. or layed into some loaded up spring poles. If this is the case the face cut should be 45've to the rear instead of 90'd to the side.
Going into the top of the tree and relieving any preasure first is a good option too. This keeps you from having to work under an unpredicatable stem, especially if someone isn't super mobil or experienced. Watch those spring poles under the top though
Thinking out loud here, nice vid Murph.