What Ann says makes sense. Tell your legman you want to try different systems. If he is unwilling to do this, try another legman. It is your longterm comfort and health that is important here. He can make suggestions, but only you know what works best.
I don't have a skin graft, but cannot wear the pin system because of the pulling on the end of the stump. I've never used the Harmony system, but have used a vacuum system. I liked the way it made the leg feel like it was really part of me, but I didn't like the way it kept it's tight fit while sitting. It all boils down to the fact that no one system is good for all of us.
I've been using Ossur's Seal-in X5 liner for the past 4 years and love it. It has the convenience of a pin system without the pulling and yet the snug fit I like as in the vacuum without that tight fit of a vacuum. It works quite well for me.