I have no experience with this guy, but I can tell you that I saw one of his tops and they're nice...
But the ones you get from Porsche (six times the cost I think) have more aluminum parts already attached. These replacement tops require the installer to remove some of the parts off the old one and recycle them. Porsche doesn't do it that way.
However, my mechanic did a great job with this top on a forum member's car. I went over to watch him work a little on it. 4-6 hours of work.
i bought a top from him. works like a champ. it's identical to the OEM. since you're installing it yourself, i'll offer my input (and condolences) as needed since i installed my own (and learned a lot in the process). if you want some help, PM me.