Ok, I found the sidebar in the Unearthed Arcana, and the fractional progression is a little different from the pathfinder unchained. I haven't had a chance to test the code so it may not work as written, but the major change is from "= 2" to "+= 2" for the good save bonuses.
As for where/how to implement it, I agree it would be nice to have it as part of the configure hero, but for testing I'd suggest using a feat or magic item you can easily add and remove to see the results.
To use the numbers you will need to add code to set the base attack and base saves to match those numbers. Something like:
Code:
hero.child[Attack].field[tAtkBase].value = babtotal
hero.child[vFort].field[vBase].value = forttotal
hero.child[vRef].field[vBase].value =reftotal
hero.child[vWill].field[vBase].value =willtotal
I'm not sure about the timing, but probably post level or pre attribute.
I'll try to do some testing later today. If you want to give it a go for testing I'd start with a feat or magic item. Use a special character at the start of the name such as "*test fractional progression" so it shows up at the front of the list. Then you can enter the code into the expression. If you use an item, I'd make it wearable (no slot) and add the following code at the beginning of the expression:
Code:
doneif (field[gIsEquip].value = 0)
The advantage to this is you can test the results (and make adjustments) without having to reload the game system or even remove and re-add feats.