UPDATE! After some weeks of intense development, I have finally released the new version of the UOC Patch, build number is N2F.
Compared to the previous version, this new one has been reworked almost entirely: many entries that point to my FF45 ESR SSE installation have been removed, shaving the size down to around 25KBs, making it even easier to fit in a floppy disk (3.5" or 5.25", your choice, for easier portability), but I've also reworked the loading routine of webpages, disabling the asynchronous panning and zoom feature, which instead of offloading the CPU, it is somehow bugged even on 45 ESR based browsers, causing an excessive spike in the CPU usage. Also, scrolling webpages while they are loading images should be smoother now, at least it is on my Tualatin RDD. I've also increased the memory cap of Javascript processes to 96MB, which seems the sweet spot between usability and performance, at least on my machine.
But the biggest news is the introduction of the UOC Enforcer. The UOC Enforcer is a custom "user.js" file that must be placed into the browser's profile folder and that tells the browser to change the "stubborn" entries in the about:config that are hardcoded by the developer, making the UOC Patch work even better. You must remember though that the UOC Enforcer doesn't let you change the edits from the about:config, so if you want to change a "stubborn" entry, you must edit the user.js file directly (you can do it with Notepad).
Therefore, I strongly suggest you to open the UOC Enforcer file and check out what are the stubborn settings, in case you want to change them in future. Most likely, you won't need to do that. While the Enforcer is optional, I strongly recommend it in order to get a better experience with the UOC Patch, as it tweaks the browser further.
You can download the updated version of the UOC Patch and the UOC Enforcer in the main post.
Please test the patch on as many machines as possible, and remember that it's offered AS IS, since I develop it in my free time, in order to squeeze some more power out of old computers and making them still useful online just like when they were new. Thanks!