You have a nice safety work but i want to point out a little mistake i can see in this video - when you you using chainsaw you left arm should be straitght (or almost) grip the middle of the rail (in down cut or upper cut) so you don't have to hold it and more importantly you didn't use the saw spike to help guiding (its help you save energy because you don't have to hold to much force on your chainsaw) - even though its down cut or upper cut you should use spike on chainsaw or cutting it nearest to your engine so your saw will steady and safer (run chainsaw at most power before cutting to help prevent saw pulling) - your ground service is standing to close to the trunk (imagine if some rope loose he will get hit badly) - i'm not sure is that tree are hardwood or not if it not you should check your chain (its cut too slow) - critical is when you vertical upper cut i can see its kicking back on you because the way you holding saw is wrong and not safe anyway i like your little blue stick so much!
