I was wondering if anyone has hit with both Polyfibre Viper and TCS and could compare them. I am trying to find a good poly to keep in stock for my customers and basically want a poly that is moderately durable, very soft (most important), and has good tension maintenance. After a lot of searching I came across both of these as good candidates. I am going to try both of them out myself, but I also have one of my customers who wants his racket restrung right now that I want to test one of these out on. Right now I am leaning towards putting Viper in his racket since, from all I have found, it has very good tension maintenance compared to TCS and they are both about equally soft. I also came across ISOSPEED Energetic Plus while searching for a durable soft string...I figure this might be a good multi to keep in stock. Does anyone have any experience with this string? Should I use this one instead of the poly in the customers racket? I am a little worried about the durability of this one. Just for reference this person is currently using full Gosen OG Sheep Micro 16 and is having no elbow problems with it (but is breaking it in a little under a month).