Hi,
there is an old method for filter design, it is especially well suited for band pass filters having center frequency Fc and bandwidth BW. It starts with circuit simulator models and then after manufacturing the filter is measured. Typically, the measured center frequency would be shifted down for dFc and bandwidth narrower for dBW. Then a filter specifications would be changed, center frequency to Fc+dFc and bandwidth to BW+dBW and filter redesigned in circuit simulator to achieve changed specifications. Redesigned filter will have characteristics very close to target ones.
Instead of manufacturing and measuring a filter, you can switch to EM simulations, it should serve you as a good indicator how you should change your specifications and what to target in redesigning. (There is an optimization procedure called space mapping that is underlying this approach, if you ask me, space maping is the only successful method for EM optimizaton) Anyway, there is not an optimizaton option within MWO EM simulator, so you will have to have some criteria how to change dimensions of filter elements.
I did some filters in that way using @DS-Momentum pair, it was extremly successful. It took only 2 iteration of the described method to get the performance spot on. The agreement with measurements was also very good.
The only difference I can see regarding the use of MWO will be that the EM structure must be snaped to the fixed grid, it might introduce some discrepancies and limitations. The X-models will most certanly get you closer to the EM results.
flyhigh