Bonding material effect on stack patch antenna

I am designing a stack patch antenna. my fabricated result shows difference between simulated and measured result.
I suspect the bonding material used by manufacturer, as the bonding material permittivity was 2.7 but patch dielectric permittivity was 2.2.
could someone suggest how to take care of bonding material effect in simulation to have similar measured and simulated result?
Thank you

What is your question? The correct engineering approach is to model what you have built in hardware, using the measured dimensions. Then you see how much better agreement you get, and if this was the error source or not.

I designed a stripline network...while designing it I just use signal line sandwiched between 2 dielectric layer. in order to fabricate it the 2 dielectric layer is required to glue together using bonding material. the effect of that bonding material is such that the performance of the stripline change. the dielectric layer are of er = 2.2 and the bonding material is of er = 2.75 because bonding material of er = 2.2 is not available.
So I wanted to ask that in such case how one should create model considering the bonding material effect. should bonding material be included in design and if so what should be the thickness ...
I was looking for someone's experience and explanation about this scenario.

Yes, build your model as realistic as possible.

Is this manufactured by a PCB manufacturer or homebrew? If homebrew, I would worry about islands of air (er=1) embedded between the boards. If it is built by a PCB manufacturer, they should be able to provide thickness values for the prepreg or glue layer. When I do such EM models of multilayers, I use the full details of cross section provided by the PCB manufacturer.