FYI, you need an effective rep of 6.67 to pay 0% refining to the corp, which with Connections 5 is 2.59 if my math was correct.

From http://games.chruker.dk/eve_online/eve_math.php

Station take when refining/reprocessing
Station_Take = Max((5 - (0.75 * Your_Standing)), 0)
For the station to take 0% you need a standing to the station owner of at least: 5 / 0.75 = 6.67


Effective Standing
Effective_Standing = Your_Standing + ((10 - Your_Standing) * (0.04 * (Connections_Skill_Level | Diplomacy_Skill_Level)))
Connections_Skill_Level is used when Your_Standing is larger than 0.0
Diplomacy_Skill_Level is used when Your_Standing is less than 0.0

- Souca -