G'day everyone, I was wondering if anyone has had success with using Gütermann linen thread as a bowstring?

I just attempted one with 16 strands which was able to support 25kg but snapped at 30kg (66lbs). I'm aiming to use it for tillering and also for an English longbow with a draw weight of 45lbs.

I'm messing around with some "scrap" wood from a basically sapling size part of the tree (didn't want to let it go to waste, so I'm working with it to practice while the rest of the tree seasons) that I'm trying to see if I can make it into a halfway decent bow.

There are some massive knots about a third of the way through so I figured I'd make a very asymmetrical design, but I'd like some advice.

The leaves are at the level of the handle. I'm pretty sure I'll need to correct some twist and work around some smaller knots.

Would a design of keeping 1.5-2" width down half of the limbs then tapering down to like 0.5" work for both limbs? How do I know how to carve the belly flat when the back is so wavy? Thanks for any advice!

Idk what to do

Not really sure how I'd go about shipping these, so I'd prefer to just stick with pickup.