When using the Fit advisor, one does not need to enter all of the six basic body dimensions. All but one of the dimensions could be unchecked to allow BikeCAD to approximate the missing dimensions. The formula used to calculate missing dimensions can be tweaked by clicking View >> Customize (or ALT-V, ALT-C). This will launch the Customization dialog box. Choose the Fit advisor tab and then the Approximate missing dimensions tab shown below:
