I actually used to fill the oil filter on my old subarus when changing the oil, it was vertically mounted upside down so no mess at all with changing the filter or filling it (why aren't all engines designed like this??).  I didn't fill the oil through the middle hole, just filed it up all over until it was full, took less than a minute so no big drama.
 
I wouldn't do the filter fill trick on a gen 2, it was bad enough spilling the oil from the filter removing it, what a poor design.  The gen3 filter is upside down but on a slight slant, much improved design.
 
Cheers