youn sure you want o shave the spacer unlevel ? as the way i read that it makes the plenum unlevel meaning the bolt holes wont have level tops.... i have the motordyne on mine and the kit came with equally sized spacer for the strut bar so all clearences are maintained so this might be worth a look rather than modding your mould.
+1 on the looking top work , keep us all posted as to how it goes as i wouldnt expect any flexing at all with 8-9mm of carbon!