Well, if it is under tension, I don't think it is as critical as you are making it out to be. Granted, I haven't built my own tent...yet...but I think you will be alright as long as the loop is under tension and it has the ability to "bite" on the stake. Personally, I plan to mimic the design of the SL5 staking points so that I can have different lengths of webbing. This will allow me to pitch it really high with a ton of space for the air to flow under the tent. Or, I can save some weight with really short webbing when I want to have the tent down on the ground in cooler temps.
Oh, and please take a lot of pics of the process and notes if you wouldn't mind passing them along once you are complete. Thanks.