Okay, Graham. I think that you have seen my various presentations on my main web page. I never know what will help.
On my resources web page for this Boost issue, I think that I have a note about the 3.5 Modifications. You should see that I am still using both a Preset file, and CSS code. I like the flexibility of using CSS code. However, some things I still do from the preset file. I think with time, I am going to move everything into CSS code. But this is probably the opposite way that I would do this if I was developing modifications that I wanted to easily share. Since I run my own Moodle and I am most busy teaching, my approach is good enough for now.
Somehow, I seem to be one of few who prefers managing (web page) content outside of the LMS. I find this much more efficient than trying to keep everything in the LMS.