OzFclass

I have a new tin of 2206H I am about to use. I currently use 45.9 of 2208 with Berger 155.5 projectiles which give me just over 3000fps.
I am looking for around the same speed as they sit nice and flat out of my rifle doing that speed.
How much should I reduce the load to get approx the same speed with the new powder?

For around the same speeds you'll find that around 45.0 - 45.2 of 2206h will be about right. That also depends on how far you are seating your projectiles from the lands and your barrel length. My old Omark was at 45.8 2208 and when I changed to 2206h it was 45.3 for the same speeds. But I had to full length the cases with 2206h.
BUT as usual start a bit low and work your way up as all our gear is different.