Not that I have a dog in this hunt anymore since I sold Rhapsody but I am sympathetic to Russ's comments. I owned a 0.5 oz spinnaker that I used for PHRF because I could afford it and
PHRF-NB did not penalize the OD rating due to cloth weight. All along I have been sensitive to those who did not want to spend the money for an extra sail, so did not want to force it, but would have been perfectly happy for the rule change if people wanted it.
One thing to consider to maintain a reduced cost for OD is to allow the 0.5 oz spinnaker in the sail inventory but take a slightly different approach for the NAs and Midwinters. Something like
"The 0.5 ounce spinnaker shall be allowed for all OD racing. The J/30 North American and Midwinter Championships shall only require the use of a 0.75 oz spinnaker, unless the race documents specifically authorize the 0.5 oz spinnaker."
This has the effect of making the 0.5 Oz spinnaker allowable for everything (including PHRF), but supports those who do not want to purchase an extra spinnaker for the NAs and Midwinters. The race documents for these events can add the 0.5 oz spinnaker based on polling the participants.