Thank you, DH-106
In that case I've found a very easy way - as there is already a part of the code to enlarge all models in the .con files I've added just one value here
values = { _("-35"), _("0"), _("10"), _("25"), _("50"), _("75"), _("100"), _("125") }
and three similar lines to updateFn = function(params)
Now I have a "0.65" option for scaling goods.