Yes to all your three questions on the new balanced rudder!
It will cure your weather helm.
You shouldn't even need to used the lockdown screw.
You shouldn't need to reef down to stop weather helm as there isn't any.
Only need to reef down if you bury the leeward ama and then reefing down will increase your speed.
I was out for four hours sailing in 10-15 mph winds and gusts of 20 this past Saturday and it was one of the best sails ever. Really a blast!!
The new rudder makes all the direrence and helps make the AI a perfect sailing machine.
Hobie as already mailed out the new rudder to all AI owners who have registered their warantees. Whatever address you put on the warantee is where it will be sent. Otherwise, contact Hobie directly and they should be able to post your new rudder to the UK.
Guess you were the first kid on the block in Thailand with your new toy.
Also check out www.kayakfishingstuff.com
for further info on the AI.
I'm list there as Punchinello.