I'm not wild about the standard way the windage tray is attached to a B engine. It seems like twice as many gaskets and twice as many places to leak.

Has anyone made a custom tray that attaches to the main caps? I was thinking of drilling and tapping some 1/4-20 holes in the area in the red circle.

I would not recommend drilling the main caps, they have the material there for a reason, and it is not there to support the windage tray.
Drilling and tapping can cause fractures, and eventual falure..
The factory used the sandwich tray on hundreds of thousands of cars without problems.
Felpro blue stripe gaskets with Avaition permatex is all ya need.

You could always run studs in the mains and run a screened windage tray that fastens to the studs like Dave Dudek runs in his Hemi.

Thanks, that photo helps a lot.

I just finished tapping my main caps so I'll decide later if I want to use the holes or not.

As for strength, the portion I show in the orange circle is not going to be compromised by a hole in the center of it. In fact, I would be interested to know just what that pad is doing there since it in no way appears to add any strength to the cap.