Tim - Although my kit is based on a Spitfire, I did read one tip on here for cutting the Herald bulkhead.
It has been suggested that you cut the bulkhead to match the contours of the bodyshell.
( Rather than the early build approaches of a straight horizontal cut. )
I also see that you are planning to re-use the Herald handbrake.
My suggestion would be to cut out and re-use the whole Herald transmission tunnel as well.
This was an early mock up from my own build with the Spitfire panel in place.
Just a thought.
Good luck, Paul.