Co-polyesters have a much lower dynamic elasticity (tension rises exponentially as the string is stretched) as compared to multi-filaments/synthetic/natural guts. Due this, they have a much higher dynamic tension(the force needed to push a tensioned string 1cm sidewards)
Dynamic tension is the true form of measuring tension in string beds.
simply string your polyesters at 5-10% lesser tension.
(eg if you racket puts the recommended tension range as 50-60, then this would mean that the recommended tension range for the co-polyesters are about 47-57).
I find that polyesters plays superior and lasts much longer at lower tensions. These are pretty inelastic strings. I try not to go above 52 pounds.
So why not go as low as possible? Well the main problem of going low tension is “ Trampoline effect ” the string bed starts to behave more like a Trampoline(Unpredictable higher launch angles) and this is a control problem.
My trick is to go as low as possible, but not too low such that you can’t handle the larger trampoline effect.
Though extremely hard hitters might have to go much higher in tension.
Unique tension properties of co-polyesters.
Its actually pretty common to find the veteran players of the game using their co-polyesters strung less then 45 pounds. Its even possible to go as low as the high 30s.
This is only possible with polyester strings because of their high dynamic tension.(although the strings are strung so low, when it contacts the ball and starts to stretch, its tension can still rise pretty high!)
Stringing your co-polyesters this way, sort of opens up a new dimension to the capabilities of your co-polyester strings.
Comfort level , durability, playability, feedback/response and tension stability rises greatly. Feel is very different.
However, your control will suffer , due to the increased trampoline effect.
This kinds of tension are more suited to FLATTer hitters or veteran players who uses short strokes and relies greatly on touch and feel.
Also, it might be a bad idea to use such tensions if you take heavy topspin swings at the ball.