OK,
Here is a link to the Offical Texel Website
http://www.texelrating.knwv.nl/, so see for yourself!
At this location, you wil find the actual weights of I-20s, I-17s, and FX-1s. Please not that the boats are weighed without spinnakers or spin gear (7kg or 15.4lbs is the offical default weight). So after adding 7kg/15.4lbs to the respective weights you get
FX-1 338.68lbs/154kg
I-17 356.4lbs/162kg
I-20 417.0lbs/190kg (not that US I20s weigh about 5 lbs more due to snuffer and larger sailplan, so average US I-20 weighs 422lbs
I hope nobody thinks that the Texel guys are conspiring against them! Face it the FX-1, I-17, and I-20 are HEAVY!