Anti skate should be in the vicinity of 10 % of the VTF. The most accurate way of measuring it is with a Wally Skater.
https://www.wallyanalog.com/wallyskater The only problem with the Wally Skater is its price. A test record is much cheaper.
I owned one of the first pair of Diva's produced. They were hands down Apogee's best speaker price considered. The Scintilla was a stop gap design with a ridiculously low impedance. The problem was you had to spend way more on amps to drive them than the speaker cost and regardless you were never going to get to Rock and Roll levels. I find it funny that a limited speaker such as the Scintilla could get the reputation it has. The Diva on the other hand was special. Flawed but special. After 6 years of playing with them I returned to ESLs where I will happily stay.
In part it was the flawed nature of their speakers that was in part responsible for their demise. Magnepan was very smart not to release a driver that was so easily damaged. You can still pop a Maggie tweeter but not near as easily as an Apogee tweeter not to mention the other ribbons are just as easily damaged.