Originally Posted by Snowflake
Wing loading and placards are the two differences I found other than the three stated purposes. Someone here on VAF suggested that the exemption allows you to build without a gascolator but I don't recall that nor would I recommend it.
The wing parameters are easily available from the plans set that comes with your kit.
It's the exemption that requires the gascolator. Personally I would like to have the option which doesn't exist under the exemption. I also like the placarding rules better under 549 as opposed to the exemption. It frees up panel space.
The wing parameters needed to calculate the wing loading are not in the plans that I see. Mean wing and flap chord? I looked and didn't find it.