Flee, it is recommended to twist an endless string. Like AK says there is a point of too much twist. I have made them with no twist and they shot fine.
They will round out better with some twist, which makes the serving area nice!
Check with the manufactures, Brownell, BCY, and they will give you reccomendations on twist.
A string that has to be twisted way too much, is a waste of material and adds alot of extra, unneeded weight to the string! Killing the performance of the shot!