ok, Yapha, it's all your fault!
You've convinced me to try this!
I used MDS. My overlay is actually a 12x12 stamp from the Number One kit ... and I think I may have 'cheated' by moving it down to only cover 1/2 the page, but I didn't like the mesh on top.
The woodgrain is Well Worn background paper as the bottom layer, so it shows through the photo, which is at 60%.
It took a lot of playing because I loved the picture so much I didn't want an overlay that took away from it.
Port Elgin Digi - Task 1 by basketballmom - Cards and Paper Crafts at Splitcoaststampers
The opacity part was easy ... getting the overlay right ... not so much!