Hi Ian
I used to have Rondar 6490.
I sounds like you have made some sensible upgrades, perhaps adding shroud levers would be worthwhile if you don't already have them, so you can release the leeward shroud downwind.
I would recommend that you dont try to get anywhere near the rig tension in the tuning guides, it would just bend the boat.
I used to sail with just enough rig tension that the leeward shroud would just be swinging in the breeze in anything above F2-3.
The mast rake figures in the tuning guide didn't work for me either. I found the boat went best with less rake than in the guides. I dont have my settings anymore, but from memory, I used to have the mast rake at around 23'10" in light to medium winds. With the front of the mast at the heel 10'10" from the transom.
There is a picture of my old boat in the registry - you can see the leeward shroud is quite loose.
www.albacore.org.uk/alb/index.php/associ...oat-register/74-6490
Regards
John