
The limits are purely theoretics (2.456 x radius) as given here:
http://media4.obspm.fr/exoplanets/pages_outil-roche/calcul-limiteRoche.html
so if one know which actually they are, please, let share this information and I shall update the add-on.
http://fenerit.webng.com/files/luatools_roche_limit.zip
In the zip there is an image file with the instructions explaning where two code's lines may be add to the extant config.lua and toolBox.lua files. This add-on has been tested with 4479 patch (globular clusters) but it is suited also for all that versions which allow the setvisible function to work properly.