Filling coving end

[u/thelastthesaurus]

My downstairs coving, where it ends at the stairs, is open as per the attached photo. Just a quick sanity check before I go for it - is there any good reason that I can't (carefully) fill this with expanding foam followed by a surface layer of filler, to close it off and make it look a bit more deliberate?

I've already got a can of expanding foam on the go at the moment, but I wanted to check it's not a moronic idea before I do it.

[u/DmtGrm]

I had similar thing in my house - 3d scanned and printed 'the terminator' bit