I have an automated intraday strategy that seems to behave well on SPY. I want to look at how it would do on the ES. Before I roll up my sleeves and test things for myself, I would be grateful for shared insights from anyone with experience of something similar. How good is the correspondence between SPY and ES price action? If something works on SPY, will it generally work on ES, too? Do I just need to transform my target of say $0.20/SPY share to $2/ES contract, etc? Thanks in advance.