Broch,
Seems like you and I have fairly opposite ideas about questions, learning and what is fun
The forum works best when both sides are presented. Some presenting the options that work for them, and others reminding everyone not to get too hung up on specific gear and techniques
I do agree that it is important to learn the principles, not just by rote, and I have seen plenty of folk on Hammock Forums discussing tarp lines where it appears they all just buy the ZingIt stuff (or similar) sold by their hammock/tarp purveyor of preference, then swear by it.
However, for some of us there is fun in the technical pedantry of optimising our equipment. We ask questions so that we can learn from the experiences of others and do not ourselves need to re-invent the whole wheel. Sure, one can use anything, for ridge lines, sharpening stones, clothes and cookware, endless options, but some do perform better than others, or at least there are pros and cons. None of us can know how someone is going to learn best when they ask a question.
If someone has a mind to learn, they will learn, whether they start in with old clothes line and mason cord, paracord, or Dynema super braid. If they don't have the mind to learn, they are as likely to carry on forever with paracord or mason line as with Excel Pro or ZingIt, whatever did the job for them to begin with.
Sub5mango.
Your idea of using paracord for the ridge will work, just not as well as a lower stretch cord (ie polyester based). Nylon stretches, stretches more when wet, and Paracord's construction is designed to stretch. By all means give it a try, if you don't like the result, there will be plenty of uses you will find for the paracord
It won't be money wasted.
2mm isn't too small for Prussic or taut line hitches on a 3mm main line, might seem so, but isn't. I don't think that Dynema is really worth the price, really, certainly not when you are starting out. I bought some ZingIt and while it is incredibly light and compact, it really doesn't work as well with knots as the 16-plait polyester lines I was using before. I can set up and take down my tarp faster with knots on the thicker line than I can with hardware on the ZingIt. If I had started out with the Dynema braid and hardware, I would not have learned the knots, and would not know how quick and easy they could be...
(I know, you can get Dynema core with 16-plait polyester braid, in which case all you are gaining is strength, not a significant reduction in weight or bulk, and more strength isn't needed just to hold up a tarp)
Best of luck
Chris