I'm doing that same thing right now. Mine isn't near finished but I have the center out and working on filling the gaps then I am going to smooth the transition from where the chrome was to the flat plastic part.
Arielgt93 is that an 02 sti scoop and is it partially over lapping the hood in the back? It's hard to tell from the pic. Reminds me of the "Mr hoodscoop"
I toyed with a few ways to make it fit but in the end I went with what allowed it to be installed just as oem. With the bolts up front and to une and groove in the back