Jeff_H is absolutely right. It really depends on the boat, and how much of a change are you looking for. The greater the change the more costly (can we say costly??) it gets.
Lets see if I can explain this...
During testing with my boat, we tried different fractional positions to evaluate the ratings as we were moving the I, the J and P to see where the rating would benefit us in relation to sail performance. (keep in mind we maintain the main un-altered), and many times we had the mast jacked up to full up postion, and got better performance.
For this we installed a hydraulic jack at the bottom of my mast, that I use to add and remove mast tension, and thus control shroud tension also, now that is a good trimming tool, let me tell you. Great upwind and downwind!!
To compensate for a lower stay, we ended up instaling forward swept spreaders, (the sreaders are inclined towards the rear but curved forward) and compensate the reduction stay height by increasing leech area, because there is a hole in the rules and the "belly" is not measured.
To compensate for the belly, my racing genoa has batens.
I hope I could explain my case, because my English... . Its a cheaper solution for what you are looking for. Also one more thing, my stay works inside the shrouds. Look in members galleries for more photos of the belly genoa with battens.
Last edited by Giulietta; 12-06-2006 at 08:03 PM.