Oh thanks exxos, I'll look into those.
I did get it boot finally. What seemed to be freezing the CT60 was when the pico initially is switched on, the fan spins for a few second then turns off. So there is power there for a second even though the momentary switch over CT63 pins 1 and 2 haven't been pressed. So then when I press the momentary switch the fans spin back on, but it is locked up somehow from that initially input of power. This doesn't happen with the real atx psu.
Anyway, so I put a 33uF capacitor over pins 1 and 2 to simulate a momentary switch which works. Oddly I tried a 7uF ceramic capacitor and it had the black screen effect. So I kept the 33uF one in.
This cap is fast enough to get the CT63 booting before it locks. I couldn't do it that fast with the manual momentary switch.