a straight line is at its longest when its 180 degrees - any other angle then it shortens,
so when adjusting the chain allow for 25mm slack then get one or two friend to just sit on the bike untill the swingarm levels
out with the front sprocket ( this is at its straightest therefore its longest ) now check to see if there is just a little play..
this way ensures the chain will not stretch due to rider weight,
I THINK ?
Its very easy to make something easy hard but even harder to make something hard easy,