Dual Boot Headaches - Can I run Mojave and an older OS?

Hey there,

So I just bought a new MacBook Pro 2019, running Mojave.

I'm trying to install an older OS as a dual boot, in order to be able to run FCP 7 for a very old but large feature film project.

It's saying it won't allow me to do this. I tried ordering OS Lion but its saying it can't be used on this machine - it won't even let me download it to try it. I'm wondering if I could use El Capitain.

Has anyone done this?

Is there any work around?

Help! This is a big project and I need to be able to access it.

Best wishes,

Kiya