Going slightly off topic. The house that I am currently working in has a plaster ogee type moulding running along the top of the strings. They had a 5mm tall crack where they meet the 120yr old strings. I noticed that there was some bounce (in and out of the wall, rather than up and down) in the strings, so I drilled a series of small holes through the strings and squirted in expanding foam to eliminate the bounce (and did so until the foam filled the crack).
I find it works incredibly well. I don't like drilling through strings and in to the wall (with screws and plugs) unless I know that there are no pipes or cables.
I am a decorator, I seldom use Easifill. In your original scenario, I too would have used foam but I would then have used one of the lightweight fillers such as Toupret RedLite or Red Devil One Time. Powder based filler tend to "blow" over time when in contact with timber.
