Personnally, I have 2 columns in my logbook
one is labelled "IFR FPL" and I log the time flown with an IFR Flight Plan
another is labelled Actual Instrument, and I log the fligt time "in the clouds"
This was done to stick with both FAA & JAA rules and practices.
Regarding the initial question, I am raising another point : is your paradropping A/C equipped and approved for instrument flying ? if placarded "VFR DAY OPS ONLY" I would tend to think it answers negatively your question
I may be wrong, but my understanding of the JAA rules lead me to think that you need the following to log IFR :
a valid IR
an IFR equipped and approved A/C
an IFR FPL
if this is the case, then you can log