[moved] Matching a patch antenna: Zin issues

Hi all,
i'm having some issues with the design of a patch antenna on a Duroid 5880 substrate (2.2 electric constant) thickness=1.575mm, solution frequency 5.8Ghz.
i've computed the following values:

The width of the patch (Wp) is:20.4458mm
The lenght of the patch (Lp) is:16.5008mm
The inset feed point (Fi) is:6.0932mm
The width of the feed line (W0) is:4.8514mm
The lenght of the feed line (L0) is:9.4530mm
The gap of the feed line (Gfl) is:0.11929mm (i got some doubt on this value)
The minimum lenght of the ground plane is:25.9508mm
The minimum width of the ground plane is:29.8958mm
The Zin of the patch is:313.6511ohm

this computation are made in order to obtain a 50ohm matchin but when i plot the report on HFSS doing:
create a new report--->rectangular plot--->terminal Z parameter---> Mag
i'm only able to obtain a |Zin|=35ohm can someone say if my data are right and if not where i'm wrong? what can i do in order to have a good matching at 50 ohm? in order to obtain a better return loss it's a good choice to trim the lenght of the patch?

Trying to be more easy (i'm new on this field and i'm not sure about how to read smith chart) this is the TERMINAL Z PARAMETER Smith Chart of my antenna, is it matched or not?