There is no recognized multi builder class called F17

The I17R class has agreed to equalize crew weight with two sizes of spinnakers and renamed this configuration as F17.

Likewise, NENSA declared the F20 fleet to be any 20 foot boat with a chute equal to or less then the Nacra NE 6.0 chute. (aprox 28 sq meter)

However,
An interesting race would be the I17R Texel rating of 103 and USPN of 66.7 competing against the F16 uni’s Texel rating of 101 but a USPN of 67.6

(The FX1 with chute is way behind the pace with a texel rating of 107 and very little US Data reported)

Note Texel is a formulae based rating which has some sweet spots. Portsmouth is a statistically derived rating based on real world performance. The amount and quality of the data determine the accuracy of the rating.