I've used both ways, but have settled on outside the shrouds. I can't sheet
as tight an angle that way, but I can still get as tight as necessary with
the lapper - any tighter and you're pinching and stalling the keel anyways,
making a lot of leeway even though it appears to be pointing quite high.
Chances are you're stalling the jib itself too. Leading the sheets outside
also make for far better sailing off the wind.
Also, I lead the sheets though a genoa block on the tracks, well forward of
the fixed blocks on the deck walkway (my telltales showed that the lapper
was far more efficient sheeted further forward). In fact, I just recently
removed those blocks all together and filled the holes with Marine-tex,
since people tend to step on those blocks and gouge the deck anyways.
I find that the under-canvassed P19 can benefit greatly from tuning the jib
sheet leads. Two of the best investments I made on my boat is installing a
masthead fly, and installing telltales on the luff of the headsails and the
leech of the main.