Custom field values

I added custom fields to tl_iso_orders through an extension. I want these fields to have a default value. But when the record is saved Isotope writes the entire record and any SQL default values or ISO_HOOK functions that change the setting get overwritten.

So ho to add a field and make sure Isotope uses the default value?

Contao 2.11.5
Isotope 1.3.4