Can't get the Detail Mask to work on my Secondary Maps

I've got a material that has a secondary normal map. However I don't want this normal map applied to the entire surface of the object. I made a Detail Mask (a black and white png file attached). But it doesn't have any effect on the secondary maps. Am I setting up the mask texture wrong?

 

I'd set up proper UV's in a 3D package instead of trying to work this into the game engine.

Just my opinion though. I'm an artist.

 

Looks like the Detail Mask works similar to the Metallic. The relevant data needs to be in the alpha channel. The secondary maps go where the alpha map is white and not show where it's black. I've saved it as a 32 bit BMP file to accomplish this. Wish we didn't have to use BMP files though, a greyscale PNG file is a fraction the size of a 32 bit BMP file.

 

Can't you use the transparency channel in a .PNG or just save a black and white image and check "Alpha from Greyscale" in the import settings?

 

I tried the black and white image and checking the "Alpha from Greyscale" and that was a no go. However the transparency channel in a .PNG file did the trick. And now my file size is 20 times smaller. Big Thanks!

 

Looks like the "Alpha from Grayscale" check box does work with a black and white png file. It didn't work earlier because I probably forgot to press the "Apply" button after I turned on the checkbox.