Because no one can stop me, updated the level. The expert challenge should be easier to get now. You will likely still need to climb over the whole building (twice) to do it, but, here we are.

Is it possible to get Perfect Gentleman without using hushcracker?

Glad to hear the Expert Challenge was hard. Also glad that you managed to do it :D
I was originally worried that it would be too easy to warrant it an 'Expert Challenge'

You could have also jumped from the roof, but it does not change much from what you did. It sounds like you did just fine .

It was hard to get the ghost part of the expert challenge because you really have to use all the delays possible, and then jump OVER the final guard's field of view from the over-hang behind him. Then again, there was probably an easier way that I couldn't fathom at the time.