How to fix a sag in a pinball playfield

Pinball playfields should be perfect flat. The smallest sag can have an influence on the trajectory of a rolling pinball.
Here's shown how David fixed a sag in his Bally Speakeasy playfield.

As you can see the sag is about 2mm, in the center of the playfield.

The support brace is made of oak because I didn't want the additional weight of an angle iron on the board. Two strips of oak at the beginning weren't stiff enough so I strengthened it with two more. It ended up not looking as refined, appearance wise, as was intended but it'll do.
The brace stays on the playfield permanently - when you remove it, the playfield will take back its sagged position.

On the left side, the support is designed to clear a switch. It then had to be long enough to reach a vacant area where 2 metal angle braces could be attached to the play field.

On the right side, the wire bundle couldn't be moved so the brace was built around it. The oak strip was just thick enough to fit between the bundle and a coil.

When the screws are tightened to flex the play field, the brace does have some give. It's not completely rigid.

As you can see the playfield is now flat. Looks great and the pinball game plays like it should.

Pictures by David B.