I've been a huge fan of gut/poly hybrids and have tried a variety of combinations in different frames. A significant benefit of gut/poly is its "casually accessible" spin. Just as power frame allow low-mid level players to hit with pace (often too much pace!) gut/poly makes it easier to generate RPMs. Good technique is still required but this hybrid clearly enhances, rather than inhibits, one's attempt to hit with spin.
The problem with gut/poly is that the poly can drop tension so fast and/or change in playability so much it requires frequent re-stringing while the gut remains perfectly fine. The other key problem is that many comfortable polys do too little to tame gut's power or are too stiff and uncomfortable.
Luxilon claims that 4G fixes the longevity problem with very low tension loss and long term comfort. And while comfortable like a soft poly it fixes the controllable power issue with a relatively high stiffness value.
This afternoon I hit with a VS Touch / 4G 16g hybird for about two hours. So I can not yet speak to durability or changes in playability. I'll add those observations later. But I can comment on initial playability in a Dunlop AG 4D 200 Tour (unmodified) strung at 55/52 (there are 16 mains, 18 crosses).
POWER AND CONTROL
This is THE lowest powered gut/poly hybrid I've yet used. It's far less than VS/PHT. It is also THE most controllable gut/poly hybrid I've tried. It made my 95" Tour feel as precise as my old AG 4D 100.
After 2 hours no problems. The only issue, at least in this frame which is a pretty open 16x 18, is that off center hits towards 12 were a little jarring at first. Nothing terrible, just more noticible than VS/PHT or any other poly cross I've tried. On paper 4G is very stiff and I have a sensitive arm. It will beinteresting to see how this ages.
I agree with others who have noticed the slightly lower spin potential compared to some other polys. For example, PHT crosses seemed better in this area. However, because 4G is so low powered, one can generate huge RPMs more safely than with softer strings. In other words, since RHS is critical to RPMs, softer strings can sometimes cause control issues when ripping a ball. With 4G I felt fearless confidence in unleashing a huge topspin forehand. The net effect was greater, safer, more controllable RPMs than with softer strings. This made shots like very annoying moonballs a breeze!
I've worked in high tech product management and it's tough. Investing in prototypes can be expensive and very risky. The key to success is a deep understanding of market and product requirements and the discipline to meet those requirements rather than cut corners.
Playing with 4G crosses today I felt like Luxilon must have been reading these boards and collecting our thoughts on gut / poly hybrids. The product is stiff enough for amazing control and yet comfortable too. It also provides access to massive spin potential like other polys in a gut/poly hybrid.
For me the real test was putting it in an open pattern frame and still achieving so much control. It's the first time that I felt this level of control in an open pattern larger than 90". I'm very curious how it might perform in an even larger head with 16 mains. If comfort and longevity pan out I may let my son try it in his Prince Exo3 Team 100.
For now, compared to the many polys I've tried, this will be my go to cross for VS mains.
EDIT: forgot to mention one of my favorite shots with this setup...taking serves and groundies on the rise. I never felt so confident doing so. Stepping into the shot I felt like I could direct the ball with great precison and confidence.