I was very skeptical in the beginning, is this a hoax, and after reading at the stringers forum there was both pro and cons. I guess I could keep on reading, but I just decided to try it out and see for myself.
Found the Angell promo code by google, and got a tension sheet for about CAN$ 20 - not more than some strings I have acquired after reading glowing reviews by posters here on TT, only to find I did not like the strings at all.
I was really not expecting a lot, had two Angell TC100 strung up with Cyber Flash with 22kg (one traditional and the other with the Sergetti tension sheets), and it was really a WOW experience for me, sweet spot decently larger, much more even stringed, a lot of the stuff the promise on their website I can relate to. However you need an electronic stringing machine with constant pull for the method to work as intended.
I found Serge at Sergetti very pleasant to deal with, I had a lot of questions and he answers them all kindly. I have now several sheets for different strings and racquets.
I can only recommend to try Sergetti stringing out and see for one self, to me it is worth the cost - but don't take my word for it, try it out and report back.
PM me if you can't find the promo code, or want to have more in dept info - you can also write to Serge at Sergetti for info.
Cheers, H