Also, if you are dead set on letting your local mechanic do this for you, that means you trust him. Since he's such an expert on banshees why can't he answer your question? There is a huge difference between the guy that can bore your jugs and assemble the top end, and the guy that has a machine shop as well as oodles of mock up cases, gaskets, plates, and a degree wheel to inspect your current mess and sort it out properly be it with port work and new domes on correct height gaskets, or figuring out how to get it to run right with out changing it.
If your Mechanic can't set up your domes or tell you whether or not to run that plate you are in the wrong spot. I ran my banshee for years with the local shop behind me and i thought it was boss as fuck. Then I finally sent it to a proven builder off HQ and holy Fuck! There is a huge difference. Just letting ya know.