I'm pleased with the end result though.
Pleased ? Pleased ???
Its Blooming Glorious ... I would be over the moon with it if it were mine!!!
Yes, I have some Carol Doak Foundation paper and its much easier to remove than regular stuff. I think its much more like what the Americans call 'construction' paper or what very young kids at school use to draw or paint on, much looser/softer 'weave' if you will ... like sugar paper.
Tell me how you chose the colours ...
that's by far the biggest headache for me, especially when its crucial to the optical illusion effect.