Masking A Video With Black Background Into A Shape (Text) But Keeping The Color

Hi, I've worked with FCPX for some years now. I know the basics (I think) I was recently asked to do create a video where we had a shape which is the text from photoshop exported as a png which is a light brown shade and a video of purple fabric moving over a black background and we want to mask that video into in the text without showing the black background and letting the color of the shape (text) light brown shade show where the fabric actually ends in the video. I can do most of that with the stencil alpha blend mode but it gets rid of the light brown color. Any thoughts or ideas on how to accomplish this would be greatly appreciated - thank you in advance!

First, Luma Key your clips of the fabric so you have an alpha channel there, before doing anything else.

And here's an old tutorial I did of this sort of trick.
www.macprovideo.com/article/final-cut/fc...side-text-and-shapes