Opk's in AM or PM?

Paige • 27| Married 3 years| Expecting Baby #1 Oct. 2019

So I'm doing the SMEP this cycle and it's very particular. It says to test opk's in afternoon. Which I have read is better anyway. Any thoughts on this?

I drink a LOT of water so I'm slightly worried about doing an afternoon one.

Also what would probably happen BD wise would be if I got a surge in morning, we'd BD in afternoon, but if I got a surge in afternoon, we'd BD in evening. So not sure what is better.