Brucat,
On your quote, "Anyone can sail in both classes with a stock (Hobie) sail. If that makes them uncompetitive at IWCA events, SMOD advocates would say that proves the point that SMOD is the way to an even playing field."
I think John explained it very well, with a couple of ommissions.
As everyone knows the boat was designed for beach rentals. As things wear out, no beach rental company is going to stay with all Hobie parts, i.e., tramps, sails, blocks, sheets, etc.
And many owners have bought used boats that have had replaced parts.
So, NO, the owner in the IWCA cannot race in the HCA because of the many possible changes to after market products, not just sails.

But, there are other HCA rules that IWCA can see no reason for. One of the main ones is the minimum weight. And yet at the same time try to push the boat as a Youth Class. That is just a conflict in ideas -- many kids weigh less than that.

The IWCA has done well without minimum weight. Yes the little people did go a lot faster downwind. And then the big people figured out a technique to get their weight extremely far forward and now the little people are only a little bit faster downwind.
Hmm! Then the little people wanted a hiking stick to get further forward. ETC. If the hiking stick were OKed, then we would have to have a minimum weight.

As you can see by this example, we are very much keeping the playing field so damned level it is sickening. At the North Americans last week we had 17 races.
Check this out: Really close races. Look at the bullets. Six different boats took a first place finish, with Woehrle(little guy) taking 5, I (big, fat guy) had 4, Stan Woodruff (old and senile middle sized guy) had 4, Scarpelli (Big Hockey Player) had 2, Sharon Woodruff (tiny little lady) had one, and Wright ( small to medium guy) had one.

I think the IWCA has it wired.
Rick