Interesting that you are using the Proxxon saw - I thought until now, that it would be too strong, so make such cuts with my saw-knife (I do not know, how is the correct term (either in english and also german )
according sellers it is called
Handsäge mit Griff / Handy Craft Saw II
according sellers it is called
Handsäge mit Griff / Handy Craft Saw II
Tamiya - Handsäge mit Griff / Handy Craft Saw II
Fachgeschäft für Plastikmodellbau und -zubehör in München
www.traudlsmodellbau.com