according the the natural attacks read out on the eidelon it says
Max. Attacks: This indicates the maximum number of
natural attacks that the eidolon is allowed to possess at the
given level. If the eidolon is at its maximum, it cannot take
evolutions that grant additional natural attacks. This does
not include attacks made with weapons.
so if you have a max 4 and you have 3 nat attacks and you take an evo that gives you 2 attacks making it 5 nat attacks can you still use all 5 because technically you didn't take any more after you went over your max?