I will give it a shot http://www.ussailing.org/portsmouth/tables06/modifications06.htm

Well you cant race F18 rating because of your curved beams and wings. I think you are going to take a massive hit in Portsmouth. Do your best, but don’t look at the scores

So you have H18M 71.4 (without wings)

For taller mast than standard .995

For non-class legal mainsail, of greater sail area* than standard main .980

Class normally without spinnaker, genoa, reacher, hooter or wire/rope luff headsail attached to a pole, carrying one or more 0.960

(Any other deviations from standard class configurations, including the addition of wings, can be assessed a penalty of at least 0.995)

Wings 0.995

Illegal downhaul? 0.995

Illegal Mainsheet blocks? 0.995

Assuming your jib is class legal.

71.4 * .995 * .980 * .960 * .995^3 = 65.8397

If you just add the class legal spinnaker to your 18-sx it would be

Hobie SX-18 spi H18SX 71.3