In my view, we have two classes: People who have to work for a living, and people who don't. Most of us are in the first class: Our wealth (net of spending) does not grow unless we are working. We're N missed paychecks away from being broke. That N may be a high number (what some people call middle class) and that N may be a low number, but everyone in this class has a similar set of problems. Yes, small-N is more difficult living than big-N, but we are more similar than different.
The second group, the people whose wealth net of spending grows without them working, live in a totally different world than the rest of us and have totally different life experiences and problems. They simple don't worry about paychecks the way the rest of us do.
So this whole "upper middle class" distinction is IMO not very important. Now, more than ever, we need class solidarity, not more labels.