I know its notoriously hard in a carbon 456 but that is what I need to do – how do you hold the frame securely without damaging it whilst pounding the headset removal tool?

If you use your hands and a 2nd person to knock it out it should come out fairly easily using the correct spreader tool.

The headset on my 456C was a right ball-ache to get out. The spreader-thingy tool didn’t really get in very well due to the shape of the aluminium the headset fits into.
I ended up making a tool to make it easier..

I use a nice long steel pipe with flared ends, long enough to hold the frame in my hands with flared end butted up to the headset cup and then whack the other end on a wooden block on the floor. In my mind this avoids any significant shocks being borne by the frame – don’t know if that’s true or even important but there you go

(a rag or carrier bag over the haedset cup stops you having to chase it round after it’s flown across the room/garden 😳 )

I-ve used an old quill stem inserted in the splayedend of the tool to make a more positive latch.

Frame in left hand then whack it.

So hold in hand don’t use my maintenance bike stand?