From the Guts & Glory Blog on the topic of cross string tension in a full poly bed: When a racquet is strung with the set tension the same in the mains and the crosses the differential between the two (as measured by a Stringmeter) is often in the 32 – 37% range. You read that correctly. The mains will measure (on average) 35% tighter than the cross strings. In the context of a full synthetic or a natural gut setup, this has not been an issue. It has been status quo. However, with full polys or poly hybrids it is less than ideal. The differential in tension with poly-based strings should ideally fall in the range of 20 – 25%…no more. When the differential in tension is brought closer together, the mains and crosses are able to work in unison with one another. When they are further apart, (greater than 25%), the mains are punished until they stabilize and come closer in line with the crosses. The result of this in the today’s world of polys is that the poly mains become overstretched and thus lose their tension and playability rapidly. One easy way to extend the optimal life of your poly setup is to allow the crosses to support the mains. This extends the useful playability by a considerable amount. Bringing the mains and crosses closer in tension offers HUGE benefits for poly players. It allows players to string at lower reference tensions where polys will shine, it extends the useful playability of the stringbed and extends the time players can get solid performance before having to restring. The easiest way to bring the mains and crosses closer to one another so they will work in unison is to increase the tension of the cross strings by approximately 4 pounds. The simple act of altering tension in this manner will definitely lead to a noticeable increase in performance in most instances. HOWEVER, when increasing the tension on the crosses it is possible to overstretch the poly, exceeding the elastic limits of the string. This is most likely to occur on constant pull machines that overshoot tension. Because of this potential pitfall we recommend keeping the tension on the crosses the same or up to 2 pounds lower than the mains and using extended pulling time before clamping off. The extended pulling time on a constant pull machine (much more difficult to achieve this effect on a crank machine) will produce the desired outcome much more reliably than increasing the set tension. We recommend keeping each cross under tension for 20 seconds before clamping off. This may seem like it will add considerable time to the stringing process, but it really does not. While the cross is under tension go ahead and pre-weave the next cross string. After weaving the cross, release the tension and clamp off. Stringing in this manner is a bit awkward at first, but soon the stringer becomes fluid in working with this method. The on court results are definitely worth the effort!