I ran test sertificate for 40 sqm spinnaker last season. Difference was 7 in GPH, so 1 per sqm. That is pretty big difference. Most logical option would be "small steps". Maybe my next spinnaker will be 35 sqm.

Update:

So I ordered and have already received North Sails NPL triradial light genoa, obviously have not used it yet, but I have high hopes.
New main will have to wait at least a year. New main and replacing my current G1 (in previous pictures) with med/haevy North triradial. (Note that light G1 I ordered is not meant to replace my old same size G1, rather than complement it, so i will have different cut same size sails for different wind strenght)

I am going to order soon new larger spinnaker also, with target area (ORC) 39 sqm. This was actually simple decision when I found out that I was missing measurement data on my ORC certificate (propeller installation measurements) and running a test cert with data from Charlotta, I found that I could run 41 sqm spinnaker and my rating would stay same with. So i decided to convert this new found rating "gift" into downwind speed, that is one of our biggest weakness.

Our main goal with those optimisations is to win Moonsund regatta.

Hope You good luck in the regatta. Waiting for pictures.