I'll have to admit it's been a while since I've read through his entire Guide, but I don't recall him talking about "flying debris" unless you break something....
If you could point me to that, maybe I could clarify what he means?
Second, about blue beam defocus, you will come to understand this better as you actually attempt to focus the blue beam. This is something I just typed on a different forum, that may shed some light on blue defocusing/focus:
"First, please don't confuse beam focus and optical focus, as these are two completely different systems, that add together to form the final image at the screen. A "focus problem" can be the result of either system being out of focus. This is related solely to blue BEAM focus, not optical focus!
Blue is difficult also for your eyes to focus on, so even if blue is quite sharp, it's difficult for your eyes to see it quite as sharp as the other tubes. This can make judging the focus of blue quite difficult, because it can be very difficult to get anything but a ballpark guess when doing beam focus and setup adjustments just looking at "sharpness." It is also almost impossible to see scanlines in the blue, even if they are there. A great strategy is to adjust focus, and in the range where focus seems good, there is usually a point where blue gets really well focused, and will dim ever so slightly. Move the focus setting in either direction and you probably won't observe any changes to line thickness, etc, but you may see blue brighten up a tad. Where it is dimmest, is your tightest focus. If you are trying to achieve more light output, then you can defocus the blue slightly to achieve that slightly boosted output. "
So you can help this attribute to help you focus the blue beam tightly, and also to get slightly higher top-end blue output capabilities if you need/want it.
Hope that helps!