as long as there isnt a card in the slot directly below your PCI-E x16 slot it should fit.
+ you have a casing long enough to hold the card
also do you mean you cant break the "cap" of the slots? just push them inward from the back. it it has a hook, then unhook it.....
and by "line" if you mean the "stip" seperating the two slots, then no, your good