Yes, there are differences, but HCA are now accepting entries based on IWCA rules.
You will be fine at Midwinters, unless you have an after market sail that is unmeasured. Even then we can check it out with a legal sail to see if you are way off.

I assume you are a Gator fan. Unbelievable improvement during the year. I am a Hurricane fan and thought they played the Gators tough until near the end of the 3rd quarter. Then they got blown out. But, boy, have the Gators have been kickin' butt since that one loss.
Believe they will take all the marbles this year.
Rick