You should be 9.5 F on the Deco last as well. I take same size for MH71/Deco/TG73/GG06 i.e. 8.5 E.
For the first 3-4 wears they were slightly tight for me in the small Toe area but then loosened up to be a good fit.
Dean had earlier told me that he wears 8.5 F in all lasts including Deco and that's how i nailed my size.
Others can confirm as well on this.