I believe the Spitfire is a grandfathered F16 boat; that is, it qualifies as an F16 and could sail in any event as such even though it does not match the rules exactly. It would be fun to see them out with the Stealths, but I understand they have a strong OD circuit in the UK. The Spitfire's record in mixed cat fleet is truly amazing (see Texel and Aruba results)--likely a testament to the high quality of the Spitfire sailors.