I use braided mason line for my tarp tie-outs. I did make mini-whoopies with them, but stick with knots for flexibility.
I have a loop of mason's line on each of my stakes, drive them in the ground and use that loop with a trucker's hitch to hold it down. Works very well, and is quick to setup and take down.
I've had no issues with this line holding knots. With the trucker's hitch, it's all held by one slippery half-hitch. Comes apart quickly and easily - one yank on the end and it's free...
When I played with splicing it, I took a piece of 24 gauge wire from a category 6 cable and doubled it. worked for me, but that stuff is Tiny.
"Do or do not, there is no try." -- Yoda