There are several parameters to full fill for a filter design. For example fpr 1 section you can use an open stub lamda/4 length for band stop filter at the desired frequency.
I think that a bandstop filter with coaxial stucture must has a main coaxial transimission line,and some open-ended coaxial resonators coupled to sides the main transmission line.
but i havent done any experiment and never seen any paper describe this.