Here's a nice report about a beachcat entering the St. Helena Cup event 13 okt 2002 which is almost exclusively a mono event with some big boats and two big trimarans.

http://www.geocities.com/f16hpclass/Report_2003_okt_13_Australia_St_Helena_Cup.html

Personally I can't tell you about H17 vs J24 but I do know that I recently sailed an exclusive upwind course against two mono's of about 7 to 9 mtr length (22 to 30 feet).

They pointed higher no doubt about that and they made 2 tacks where I had to make 3 but I clearly overtook them on speed and sailed past them by the same they were leading me at first in about 90 minutes. I think they were leading me by some 6 kilometers. It was during a small trip up and down the Dutch coastline I made a few weeks back. I was single handing a 1975 Prindle 16 with jib and was just trapezing in sizeable but not violant chop. I was definately steering over the waves to minimize the waves hitting the lip on my hulls.

I once sailed against a very modern 12-18 mtr yacht and that baby was really hard to catch upwind on the same P16 but then doublehanded in less wind.

I think that you can distinquise two stages. 1 is where the mono hasn't reached its hull speed yet. Here the cats have a much harder time upwind and downwind. Stage 2 is where the mono has reached it theoretical hull speed and can't go faster will the cat can. Here you'll smoke them hands down.

Wouter