Serving is a very interesting topic in my opinion. It's not just to protect the string, there are a couple more interesting uses for it here and there. Reason why it comes in so many different diameters for the same material, but more about that later.
I never really thought about it until now that it's right in my face. My guess is, to avoid such drastic separations in the loop, a thinner serving should be used to get a tighter wrap pattern. This will give less separation in tighter bends that the string is dealing with when thrown over the prod tip. Not sure how you serve the loops closed, but think it's worth mentioning that serving *towards* the loop will help put pressure on the ends of the loop's serving too.
As for the center serving, like in the videos - serving over a stretcher is the cure. I also battled these separations at one time and it's all good now.
Now about the variety of uses. It mainly applies to fine-tuning the center serving and it's relation to the nock of the bolt.
Since we are dealing with different diameter bolts, different bolt groove dimensions, and different overall string dieters due to different strength prods and string materials - all of this has to be calculated to work properly - so the string contact the bolt dead center (theoretically correct approach, but I've also heard it should be just a tiniest fraction above center, but again - *heard*
) Now to fine tune this contact point is where different serving diameters come into play. A thicker serving would give one a string with that sits higher on the track and is used to adjust the string center to bolt nock center contact if the string contacts it too low. Same for the smaller diameter serving - which brings the string lower as opposed to the thicker one.
...kinda like that, but that's match grade stuff. Still, it's something to throw something on the forum...if it comes in handy in the process, all the better.
PS: Basilisk's stuff sounds very interesting. Now you did it man, now you *have* to find a way to show us.
...just messing, anyone heard of this before?