Hi HyReZ,
thank you for your response. I'll give it a try.
Eidt: plugin looks promising, though has 1 bigger and 1 smaller drawbacks:
Offsets are in pixels, so shadow is IMHO far enough from plane if plane size is smaller, which is not that big deal, since final images are 48*48 pixels anyway, so they can be crated nicely even from 450*450 let alone my 1300*1300 px.
Bigger issue is: plugin is only callable from menu, not by key combination, which would be more difficult to achieve properly from script. Setting shadow once and then resizing doesn't really work.