I had the chance to hit with a VS Longevity / Black Fire hybrid a few times this weekend. My son is using it in one of his frames and I liked it so much I'm having one of mine strung the same way. TW's senior playtester, Chris Edwards, described Black Fire as comfortable and low powered and that is spot on! Best synopsis of Black Fire in a gut/poly hybrid: it performs like a spinnier version of a 4G cross and is easily as comfortable if not more so. Where 4G dents pretty faster than Black Fire and provides less spin potential than other poly crosses BF is still smooth after hitting a couple of hours each on Friday, Saturday, and today (total ~ 6 hours+). In a gut/poly hybrid I believe that it feels like it drops tension a little more and a little faster than Chris's full bed test but even then it's still very control oriented as Chris described. We had it strung as Longevity/Black Fire 17 at 54/48 and it's one of the most comfortable hits I've experienced. Due to some perceived tension loss I'm having one of my frames strung at 56/50. One benchmark I use in judging a new setup is my result against "pushers". As a low to mid-level player can I generate controllable pace to hit winners without giving up enough UEs to lose. My wife is the ultimate pusher. She won tournaments in high school, took several years off for career and kids, and has been playing mid B to low A doubles since earning several bag-tags along the way. If I can bagel her confidently at will by hitting winners off her crafty, low-pace shooting I know I have a potential keeper. This morning I was able to accomplish that goal. The primary benefit of Black Fire in this hybrid is its combination of low power and tremendous spin potential which means a noob like me can hit harder for even more spin without hitting long. Yes, it's a crutch, and it's effective. It was especially telling on serve. This morning my wife said I was serving with more pace than usual but they were staying down. Spin + power = winning combination. Durability remains to be seen but so far I'm loving the comfort. Certainly more comfortable than pre-stretched Focus Hex or 4G. It's like a combination of the two: it provides the control and comfort of 4G with the spin of Focus Hex. We'll see how long that control lasts, especially in ATL's hot spring temps (80s later this week). But even if we need to bump tension to 52 and maybe pre-stretch a little this could be a keeper. Still in the honeymoon period with Black Fire but if Chris's reports are accurate I'd be very happy if this lasts as a cross for 4 weeks (he reported 3 weeks in full bed and poly crosses in a gut/poly usually last longer).