As far as I remember this spare Line from flysurfer has not a very High breakload , something like 200 kg. On top of that on your inner knots , the Line is not doubled and will be the weak point. I think it is ok for light weight rider for free ride, or hydrofoil but i would be more doubtful for big jumps or freestyle on TT with a heavy rider.
If you have pure dyneema rope, at 2 to 2,5 mm diamètre, i think you will gain safety with a high Minimum Breaking Load aroung 400 kg.
Best, If you can, not difficult, is to splice a dyneema loop: solide, not knots, beautiful
Lots of tutorials on youtube.
Or juste à simple splice at each extrémity.
If you are reluctant to splice, look at the " fishman knots" more résistant than your "8 knot".
(i personally do 2 turns instead on one on the picture for each half knot
Since this knot is a way to close a loop , only one knot provides the two loops directly at each extrémity.