It wasn't all that hard. It was time consuming. I just started slapping 3/32 sheet on and went where it took me. I have about 8hrs in this baffle. I worked on it most of yesterday and today. Still need to paint it black. It clears the cowl by about 1/8" or 1/16" all around. I'm going to use some cockpit coping (foam rubber) and run it around the outside of the baffle to give me a seal and some vibration isolation. I don't want the cowl touching the baffle and I'm hoping the foam coping will provide the air seal I need without letting the fiberglass touch the balsa.

See the whole thread here, if you're interested. There's a lot more pics of the baffle in that thread.
http://www.rcuniverse.com/forum/m_7778877/tm.htm