So for anyone who is keen for an update, I managed to get out this afternoon with a guy I've taken a few lessons from before. He had a go of the board and confirmed it was just a skill issue (no surprises there lol). He also had an axis short fuse and I was able to give that a go with my foils, and for those of you who thought the greater stability of the longer fuse meant I was overcorrecting, I think you're right. Once I worked out my foot placement it felt better. So now I've got one of those on order.

I also focused on (and had some success with) narrowing my stance and moving the front foot further back.

I'll stick with the rest of my gear for now and continue to work on the skill issue. Thanks all for the input!

Hi Dieseagull, I've just read through this topic as I have a bit of trouble with pitch control myself. I noticed that you have 2 front foils that both require a black fuse, i.e. much different from the (red) windfoil fuse. That is, the black fuse has a different shaped head (where the front foil attaches). I am pretty sure that neither of your foils will work at all well on the windfoil fuse. So I agree that getting a black fuse, either standard or short (784 or 703) would be a priority. P.S. I just checked on axisfoils.com and notice that they have a black windfoil fuse. I now assume that your windfoil fuse is a black one. If so, please disregard above comments on that.
My other point is that I had to spend quite a while using an old 1020 foil which was huge (2050 sq. cm and very thick) to get reasonable pitch control. I tried it with my (red) windfoil fuse, but found it was easier with the standard fuse. (I think, as some commentators have suggested, that it was too slow to react.) I did find the 500 anhedral stab helped at first, then I graduated to a 400 freeride. I should admit that I am 74 y.o. and have lost quite a bit of my sense of balance, so you might not have to go through all that! Only now (after 18 months wingfoiling) am a graduating to an HPS 1050 on a short (black) fuse with the 400 freeride stab. But it is a bit like starting again, having to learn better pitch control. I'm sure you will pick it up more quickly than I have, but you might find the path I took to be informative. I certainly think you would find the HPS 1050 to be a good foil to start on from where you currently are. I am amazed at how many blogs I've read that credit the 1050 with a breakthrough in pitch control, etc. Good luck with your journey!