Same here, no specific suggestions. I will say this, I am one of the weirdos who loves the flavor in the Siren V2 (24 and 22 mm) while there are several folks very disappointed in the flavor (compared to the Siren V1). Perhaps they had it longer, perhaps since I don't have the V1 (with all its issues) and so don't have something I am "super familiar" to compare it with. I will say that (for me) it shines with sweeter berry or fruit juices.
You will need to continue experimenting, but just because a lot of people like something, it does not mean that everyone does. So you may never get it to the point of your "expectations" but I am sure as you experiment, you will find room for improvement.
Best of luck,
Anna