I had to go back and find some additional info from one of the better carb guru's. hence the .1 above mating surface, he does not reference it as mm, but as the point 1 which is one tenth. Myself, never had a float issue with stock or 42hsr carb. I'm only referencing from all the posts that I have read over the last 4.5yrs, and what seems to be the fix for gas puke, I must have read well over 100 posts on this issue, and the level recommended seem to do the fix. Could not find reference in manual either as far as front or back for mating surface measurement, but everything I have read by others have been rear, probably because and you have found the rear is the higher side. the manual does call for 1 or 2 tenths over mate surface, hence, I would side with the no more than the 1 tench to err on the side of caution.