waveguide filter design

I calculated the size of a TE101 mode caivty.and calculated the coupling coef between two identical cavities(2mm thick iris).then using the direct coupled method to got the size.but because the coupling coef is not very accuate so
the simulated resoponse of the design is very poor.nearly cant see the filtering figure.I hope to use screws to tune the frequencies of each cavity and to tune the
coupling coef,and hope to tune out a good product.is it ok?
I really have no time to optimize it.so i use the method of coaxial cavity filter.
thanks for your view.