As the Wilson Watt/Puppies evolved from the original WATT's thru to the W/P 8's, the knock on them were 1) brightness in the mid and upper mid-range and an upper bass "hump." I don't think you can get away from these characteristics entirely especially in the 5.1. The W/P 6, then 7, 8 gradually tamed some these characteristics in each successive generation.
I remember hearing a demo at an audio show years ago (1996) with the 5.1 driven by an all-tube Jadis system and it was really magic with no brightness or any "hump." Of course it was set up by the late Brooks Berdan with an all analog system (VPI TNT). Brooks was a master. It won the contest for Best Sound in Show (Stereophile Show, if memory serves). The secrets to taming the sound are 1) getting the right associated equipment (tube stuff seems to help), 2) room treatments, and 3) very careful speaker positioning in your room. I use solid state electronics in a pretty "bright" room so some well-recorded records sound great and less well-recorded stuff sounds truly awful. Raising the speakers up with the Puppy Paws will help diminish some of the upper bass 'hump" at 80-90 Hz..
I suspect your new drivers will settle down with time. Toeing the speakers out slightly more than Wilson recommends also seems to tame down the brightness in my system at the price of imaging. Finally, cabling makes a difference too. I've been using Transparent Reference for many years and they seem to work well in my set-up although they're outrageously expensive.
It's a lot of work but when it's done, you can sit back and enjoy the music!