In the section for poor equip you can read "Weapon. 2 sock heavenís light. Ignore the +skills on it,it has to have 2 sockets so with the addition of 2xshael it will hit max smite/zeal speed with the use of fanaticism."
V3 of that calc is here. I get 58 IAS needed for 4 FPA Zeal with both calcs so you must be doing something wrong. Did you remember that it already has 20 IAS or maybe the level Fanat you chose was too low?
It's worth mentioning that if you've got 20 IAS elsewhere (like on Highlord's or Laying of Hands) then you only need 1 Shael in the weap.