General pot odds question

[Raemius]

I hold A[img]/images/graemlins/spade.gif[/img] 10[img]/images/graemlins/spade.gif[/img]

Flop Q[img]/images/graemlins/spade.gif[/img] 7[img]/images/graemlins/spade.gif[/img] 2[img]/images/graemlins/heart.gif[/img]

There are 9 cards that will make me the nut flush, there is about a 20% chance of me making the nut flush by the river. Assuming there is $400 in the pot, what is the largest bet I should be calling?

I think I definitely call anything <$100

Do I call $100, $125, $150?

I'm thinking even with implied odds, anything above $125 is -EV

Am I correct here?

I have problems seeing odds as a:b and tend to automatically think percentages, that's why I'm asking.