Welp, I ended up ordering an S2 last week and it's been installed for 4 days now. My results thus far for the new C5 have been mostly inconsistent vs my Taylor testing.
Over the first 4 days:
CH: 235, 442, 393, and 517! My Taylor testing is consistently around 350-375. I guess I'm supposed to take the 4 day average!
CYA: 104, 132, 122, and 150. My Taylor results are consistently around 70-80
TA: 84, 77, 87, 93. Taylor consistently gives me 70.
PH: 7.7, 7.8, 7.8, 7.8 -- this is spot on with Taylor at 7.8
FC: 5.8, 8.9, 7.4, 6.2 -- Taylor has been 7-7.5 each day.
I've reached out to WG for input... not sure why it would be this variable. Also, there is no free lab test in the box with the S2. Not clear if I order the 0.00 kit online (pay $8 shipping) and send in I can still get a free test.