I think the hard part, that high up, will be getting the saw positioned where you want it on the branch and then the teeth turned the right way against the branch. I do hope it works for you!
X2 Ive done a couple jobs with them. If you are not good at backing it in (like me) the rental place may deliver it to the spot you need. They may also rent for a half day. I also have a 14' heavy duty aluminum step ladder as well as a pole saw that is 10' long. Standing on the 10th or 11th rung I can reach rather high. Mine is a Dewalt battery saw and haven't used it on anything that big. Probably not an option for you as I've worked on ladders most of my life.