Hello,
I am an electronics and telecommunication engineer and my major is wireless systems' design. So far I have designed many antennas and their related parts such as matching circuits, filters(lumped/distributed), power dividers, phase shifters, etc. and I use CST Microwave Studio Suite for most of the design I did hence I am very professional in usage of the program. So I am sure that I can help you with your project but the thing is the dimenions are a bit problem. This antenna can barely fit to this size so you may have problems with radiation patterns since the larger ground's and substrate's dimensions are better for radiation pattern however just let me know and I will do my best to help you.
Best regards