I started out with a stringer made from sail-cord with a breaking strength of 150 kgs.
Now.. I just put the bottom nock on the inside of my boot and by pulling the centre and puching down on the top limb I work the top loop to and in the nock.
Works like a charm ( on both my 100 lbs Fairbow and my 110 lbs Stratton warbows. )
Also 150 kgs is guaranteeing no unwanted 'mishaps'... Stringers from a 'regular' bow-shop are NOT suitable for warbows
)