Been there. Done that. Doesn't work. Those of us who REALLY know Kalman filtering tried that over 20 years ago. In fact, a correspondent from the B-Team who shall remain nameless told me Kalman himself tried it. If you wonder how he did, he still works for a living.
Preaching to the Kalman choir, the fundamental problem is that there is no measurement noise and no noise in the "signal". So you don't need a Kalman. Further, there is no way to create the required physical model because price doesn't behave "physically". If it did you could just calculate as many derivatives as you need for accuracy and project forward. Tried that, too, hahahaha! There ARE underlying market mechanics that you can model mathematically that affect price, but pure price don't cut it. Fucking mathematicians. There are days I wish I wasn't one. Just led me ass-tray for years in the markets.