Deffo needs more downhall, when wind picks up for the 6 or 7 I totally collapse the ncx so the top looks like a bag of crisps but it works a treat. I only use mast extenshon as a guide best way for me is to play with the settings till it feels right
Recently decided it was time to replace my 2008ish twin cam 6.5 NP. Been a great sail, easy to rig, no fuss, good thru gusts and lulls but last time out ended with a large slit thru the main panel. Decided not to replace the panel due to the age of the sail. So started having a look at 2nd hand equivalents available. Not too many NP's around that appealed. Came across a 2016 NCX 6.5 demo at a good price. With all the current hype on the NCX, decided to buy it. My main concerns were the non cams and the opposite side rigging. This was after getting over having to buy a Severne mast to rig it on. I have an old (2008ish) 6.0 Ncx which rigs on my Pryde masts perfectly but only ever gets used if my son decides to come for a blast. So first 15-20 day rigged up the new sail. Decided I'd better rig it opposite side. What a s&@t show. Took me about half an hour of cursing. Amazing how you get used to rigging one way. Got it rigged and wasn't happy with the profile but with a fast outgoing tide decided just to get out there. Wind had dropped, went out and back didn't get planing and packed it up cursing and deciding to ditch it for a 2 cam Pryde. That was last weekend, so with no wind today decided to rig it up at home. My conclusions today:- 1. Yes , because it doesn't have cams you can rig it either side, what a relief! 2. Got the batten tensioner out and found it was already fully tensioned on lower battens and was happy with the profile when taking more time to look at it. 3. I always gauge down haul by looking at the sail. I had floppy leech down to third batten and resultant extension with the 430 Severne 45% mast was 35cm. (Printed on the sail is 31, that's big difference, don't know how they come up with that number!) Now I'm happy to give it a second go, now just need some wind.
Note that some non-Severne extensions do need a few extra cm. I've found the Chinook extensions need +4cm to get the same length as the modern Severne extensions. 
Select to expand quoteandysails said..
Note that some non-Severne extensions do need a few extra cm. I've found the Chinook extensions need +4cm to get the same length as the modern Severne extensions.
Sorry I don't understand what difference the brand of extension makes. I got a tape measure and measured 35 cms of extension past the bottom of the mast to get what I figured was sufficienT down haul for the sail. It's no issue to me because I don't rig according to what's printed on the sail anyway.
