Yeah. Installing a newer glibc is not recommended. I once tried, and ended with several problems. I just upgraded.
I don't know how it is working on ubuntu right now, but the past upgrades of the system I did using Fedora were pretty much seamless. I just faced some problems related to the graphic controllers, but overall, everything worked better.
Another option: how about adding an HDD (or SSD) and installing there a newer version?