more on old IOR boats
I also have owned a 1973 S&S 25 foot IOR era design. Mine was a Northstar 500 quarter tonner. The description of your boat very much matched the Northstar that I owned. Both your boat and the one that I owned were very early IOR-1 boats, which tended to produce reasonably good boats compared to later, more modern IOR-II and IOR-III. (Webb Chiles''s Heritage One Ton is also an IOR-1 boat as well. I would also like to point out that Webb Chiles would not exactly be a good role model of a sailor chosing sensible offshore cruising boats given his track record of choices in the past.)
In any event, while I somewhat agree that smaller early IOR-1 era boats were generally more robust and more seaworthy than later IOR boats, my experience with my quarter tonner was somewhat different than yours. On the Quarter tonner that I owned, there was a tendancy to aerate the rudder at moderately flat heel angles (somewhere around 35-40 degrees) and for the boat to round up at that point. While the boat was nicely balanced a flatter heel angles (say under 20 degrees) leading up to the wipe out, the boat would rapidly develop higher weather helm loads.
Downwind the Northstar had a tendancy to roll wildly under the chute if there was any seas running. So much so that it was possible to roll the spinnaker pole end into the water. Power reaching under the chute was pretty much of a white knuckle experience as the huge chute tended to depress the bow and make the boat want to round up and yet the huge overlap of the chute made diving down in a gust a bit of a risky activity if you were short handed.
Probably my biggest gripe with boats of this era is their sail plan proportions. On my Northstar, like most of the IOR boats that I have sailed, the mainsail was tiny and the jibs were huge. This meant frequent sail changes. To get any light air reaching or beating performance on the Northstar, we used a light #1 genoa (170%). This was a wonderful sail for those conditions but somewhere around 6-8 knots of wind was beginning to overpower the boat and we would have to switch to a heavy #1 genoa (150%). That sail was overpowered at roughly 12 knots and so we would either shift down to a #2 (140%) or else a reef in the main was required, which was slow and gave the boat a little bit of initial lee helm. The #2 was a good sail in winds from roughly 10 knots up to the high teens and then we shifted to a working jib that was just a tick below a 100%. With better sail cloths perhaps each of these sails would have had a wider wind range but to sail the boat with any kind of reasonable performance at all, expecially when loaded to go cruising meant a very large sail inventory or else a lot more motoring than I would prefer.
And that brings me to my final point on these boats. Because of the IOR rule, these boats tended to be very sensitive to the amount of weight carried aboard. A 25 foot IOR 1 boat was made to be sailed by five or six crew members, somewhere around 1000-1200 lbs of crew weight and when going up wind that crew was expected to be on the rail. Fully loaded to go racing these boats would tolerate roughly a ton of live load (crew and supplies) after which they became harder to handle. That is a comparatively small payload for a 25 foot cruising boat.
I guess my point here is that while you have successfully proven that you can cruise and live aboard a small IOR-1 era boat, I would suggest that I strongly agree that there is quite a bit of variablility in the suitability of even S&S designed IOR-1 boats to being used as cruising boats. I will also suggest that some of the designs from that era that emerged based on the MORC rule, and from the later MHS (IMS) rule produced boats that are easier to short hand and perhaps more seaworthy as well.