you are right, the choice to give 2 (different) downsampling factors is not very useful there. In fact the software is already outputing square pixels in geographic coordinates (that’s the reason why if you give 2 different numbers, the bigger one is ignored). We will correct it in the future.
So, don’t worry about the shape of the output pixel. If you want to change the proportion of the pixel in SAR coordinates, use the multi-look factors in the insar processing options.
if you want to process 1 single interferogram (usually you do it for the sake of trying and testing) then use the “Single Interferogram Processing” module.
However, when you want to process a series of interferograms in a row, all of them with the same options, you can use the “InSAR Parameters Selection” module, and then you launch the button “interferograms processing” in the “site processing” window, “insar processing” frame. Such a button will apply the options chosen in the “InSAR Parameters Selection” to all interferograms loaded in the current images graph (visible at the top-left corner of the “site processing” window).
Please consider that we are talking about a multilooking factor acting on interferograms. If you want to display your SAR data with a different proportion in range and azimuth in order to see a square picture, you can change the axis ratio using the corresponding button (axis image/axis normal) in the “advanced parameters” module: http://sarproz.com/manual/adv_param.html