Hybrid update - Since my main problem has been severe notching of the mains, I thought maybe a softer cross would reduce notching. So I just finished trying a hybrid of Lux4G 16 (287 stiffness) with Prince SynGut Duraflex 16 (177 stiffness). The verdict? It appears to be the case. With a full bed of Lux, my mains were notched halfway through within 3 hours. At the same 3 hour mark with the syngut, I only had less than 10% notching. However, at that point, the syngut was beat up pretty badly. By hour 5, the outer sheath was completely gone in the sweet spot (that's kinda funny looking). I think that sped up the notching, so that by the end of hour 7, it was unplayable. Anyway, so syngut is soft enough, but not durable enough. I will say that this combo played better overall than a full bed of lux. More power and comfort, in this case better durability because of less notching, and of course it would be much cheaper.
With this in mind, I'm going to try 4G with a softer poly. I have strung up Spin Cycle (206 stiffness) with 4G, and will report on that next. However, I'm thinking a soft, smooth and round poly would work best. Mining the TW database, it looks like Topspin Cyber Flash 16 might be ideal. It has a 185 stiffness, has decent power (85), and is about $3.50 a set in the reel. Anyone used that as the cross in a hybrid?
I might would try some Pro's Pro, but I can't get any stiffness numbers for them since they aren't in anyone's database.