Removing bottom case on macbook pro

I'm trying to remove the bottom of my girlfriend's macbook pro 15" to replace the HDD with an SSD. I've undone all 10 screws but when trying to lift the bottom there's some resistance somewhere near the front of the case, almost like it's been stuck down with some sort of adhesive. Is there anything I'm missing or do I just need to pull it harder to get it off?

There's usually 2 locating pins in the middle, if all the screws are out then it will lift off with a little pressure. Lift from the back (side with the black bar) and it'll pop off.

There's a good chance that one or both of the pins will detach from the back cover, they can be removed and discarded or super glued back on to the cover for reassembly.

Brilliant, thank you. It popped off with a little pressure