Volume and Mute Button Depth is Off

I'm in the midst of reassembling my 3GS after replacing a cracked housing, and the volume and mute buttons don't seem to be protruding far enough after putting that assembly in.

I've tried and retried 10 times, with the same results each time. They both sit almost flush.

So I'm wondering - is this normal? Do they get pushed out to the correct depth after everything else is in the phone and is pushing on them?