Well i think SIW simulation in HFSS is easy, Please be specific what is the problem? Just make substrate of appropriate dimension and add via post wall on the sides assign them perfect E. for version 10 or less you need to subtract the vias from substrate later dont require this step. Assign waveport on the feeding faces of SIW.
I'm beginning with this technology, i not understand how to strat with SIW technology in HFSS. Please can you gives an example of HFSS files to introducing to this technology.
I use HFSS 9.2 and HFSS10.
Question: this versions (9 and 10) integre SIW technology (librairie)??!
check attached file for a 60GHz SIW straight section. This is made is V13 and i am afraid it may not open in older versions. I am attaching a photo of the structure which will help you if you could not open the design in HFSS.
Hope it helps
BR
FS