Hi Crabstick. Yes; the original Boost LV really needs a big aggressive rudder. The X has the rudder 100mm further forward. This has made a big difference. It is even more manoeuvrable and much more resistant to broaching. I'm only using a 7" 30° rudder even in rough, choppy conditions. I have a downwind specific rudder for big conditions though. The bucket is even more comfortable (for me) than the original. It does still have the same tendency to nose dive though. Like you I have learned to try to stay high on the wave and I've become very active with my body position. I find it's not so much how far I lean back but how fast I lean back. If I'm sliding too fast down a big wave or I want to jump onto the next run; I lean back hard and fast just as the bow looks like it's about to go under. It's almost like pulling hard and fast on the handle bar of my mountain bike when I want to jump an obstacle at speed. This tends to keep the bow from diving. I also use a good wave deflector which helps enormously. I am very happy with the low volume bow because it is so resistant to cross winds which I often encounter. It's a compromise but it works for me.
In pure downwind conditions; the V9 is brilliant. Even in rough conditions it just skips from wave to wave like a champion. There are obviously plenty of "faster" skis but I can't always apply full power when I need to in such boats. The V9 is buoyant and really confidence inspiring which makes it surprisingly fast. I still needed a wave deflector in proper downwinders. Not that that is a problem. If the bucket was not loose and uncomfortable for me I would have kept it. I can't be arsed with padding buckets out unless everything else is perfect. If the bucket is comfortable for you then I'm sure it's the right ski for you.
If this bloody COVID 19 hadn't turned up I'd be heading over to Perth in November for my sixth Doctor. I love paddling over there. In fact I just love hanging out over there. I usually head down to Mandurah for a few days after the downwind week and do a few Cut Runs with the local crew. I then head down to Busselton for the Ironman or the half if I haven't been training properly. Not last year though. And not this year either damn it.
Current boats
Epic V10L Ultra, Carbonology Sport Boost LV X, Fenn Bluefin, Nelo 510, Fenn XT double, Nelo 600, Expedition Kayaks Azure
Previous boats
Spirit PRS, Fenn Swordfish, Fenn XT, Fenn Swordfish S, Think Zen, Epic V10L Club, Epic V9 Ultra, Carbonology Sport Boost LV
Most with DK rudders