Not sure if I was imagining this but the stringbed seemed slightly stiffer this time round. I hoping that was just due to having removed a number of the crosses and re-pulled tension on them rather than the strings starting to go dead. The last cross above the gap also showed a bit of movement this evening without going back into the place. The other strings were okay.
I'm not one that subscribes to the "going dead" theory. Strings continuously lose tension and thus become less and less stiff as they age are are played with. I would be more inclined to think that the slightly increased stiffness you felt was related to the string movement you noticed. If the strings are getting stuck out of line it means they are starting to slide less freely. They could be dirty, scuffed, have lost too much tension to slide and then snapback. Hard to say. But if they aren't sliding and snapping back you'll get less dwell time and more impact shock. I actually think this is what happens when people say polys "go dead." But who knows?
I'm going to have restart this playtest with a new set. Bit annoying really because at various times, I was really enjoying hitting with this string/racquet combination. During my first set hitting with the ZX earlier today, it actually crossed my mind that I hadn't had this much fun with the 6.1 since the time I strung it with a Wilson NG / Alu Rough hybrid. The ZX/6.1 combo was that satisfying.