It didn't seem to make any visible difference. I was riding in the C group and managed to overtake between 6 & 8 riders in each 20 minute session.
I was the only person in my group with a 400. All the other guys were on 600's or 1000's.
Now, there are not many things that feel better than overtaking someone on a new CBR / GSXR 1000
I now need to decide how I will seal the holes in such a way that you cannot see them

