Replying to Foils' true centerpoint???

Everybody who have the 174 Foils help me figure this one out. I know this was discussed in another thread, but I'm still confused (sorry for that)!

I have them mounted at recommended.
I did all the measures a few days ago and here goes (these lenghts are from mid sole to the end of the tip/tail):

tip length 87,8cm, tail 84,8

If I measure the length from the +3,5cm forward mount, which is marked on the ski with a very dim line across the whole waist it goes:

tip length 84,1cm, tail 88,5 (tail longer than tip?!)

Appreciate all the thoughts on this one since I'm pretty new to Newschool!