Hi @ian57 - thanks for getting back to me.
I modified system.fbcp.enabled=1 as suggested.
I also made the following changes to recalbox.conf:
#global.videomode=DMT 87 HDMI
I also added the following to the end of /boot/config.txt:
#forcing HDMI output at TFT screen resolution to be able to make the FB copy
hdmi_cvt=320 240 60 1 0 0 0
# working config for speed
# 900 Mhz -> 48000000
# 1Ghz -> 35000000
#modification of the speed
This pretty much matched what I had done before and I'm getting the same results.
The new xmas boot vid starts but just at the point where the xmas tree is expected to show the screen goes white and doesn't change.
I've tried a RetroPie install and it worked so I know that the screen is working ok.
Do you have any suggestions on what I might try next?