Penthouse 100% Problem - Solved

Anyone who has tried to get 100% on the Penthouse level and kept failing, I have the solution.

Basically you have to knock out the old Dvorak keeper without letting him see you. For some reason (and I guess it makes sense given how Sam is supposed to be stealthy) if you're seen by the old man it counts as being seen by the enemy. Also if you knock him out you get different dialog, which in my opinion is a lot better.

"You probably don't think I'm a very nice guy, do ya."