Seeking advice re. evolution-based arcane familiar archetype

[Doskious]

I'm trying to whomp up an archetype for Arcane Familiars that, mechanially, gives them an evolution pool based on their master's primary casting stat modifier.

Unfortunately, everything I've tried to achieve this via Eval Script has failed one way or another: if I time the script in the PostAttribute phase, it can identify the right number just fine, but the number of evolution points that the familiar displays appears not to change, but if I time the script in the PostLevel phase (or earlier), while it gains the ability to modify the value that determines the number of evolution points, it loses the ability to determine the master's casting-stat modifier...

The following code executes on the familiar as the "hero" thing. Everything I can find about bumping evolution points seems to execute by the PostLevel phase, and I'm starting to think that what I want to do is not possible to do in HeroLab (which strikes me as both silly and unfortunate, if true).

<eval phase="PostLevel" priority="10000" index="2"><![CDATA[
  var bonus as number
  bonus = 1
  foreach pick in master.hero from Class where "sClass.arDFamMorp"
    debug eachpick.field[cAbbr].text & ": " & eachpick.field[cSplAttBon].value
    bonus = maximum(eachpick.field[cSplAttBon].value, bonus)
    nexteach
  debug "bonus: " & bonus
  perform hero.findchild[BaseRace].setfocus
  focus.field[rGiveSpec].value += bonus
  debug "Evolutions: " & hero.findchild[BaseRace].field[rGiveSpec].value]]></eval>

Any insight into how to overcome this conundrum would be greatly appreciated...