breakdown in microwave filter

For calculation a handling power of filters I wrote the next MathCAD programme. Using this programme you can find minimum distance between critical points in filter's structure. For example in combline filter, such points are top pieces of rodes and nearest part of tuning screws , where is highest level of E-field.
I use this method at a previous stage of design . The final decision about filters handling power you can get after EM-simulation.
I'm interesting other opinions about this problem.

does anyone use hfss to calculate the handing power of filter?

Any matlab code for calculate the stored energy inside each resonater ? And do you think this method is accurate enough in the condition room temp , 760 Torr?