5/16 Braided Line On -6 An

I have a braided line that looks to be 5/16 (-5?) And where it needs to go has a -6.

I'm curious to know if I can make this happen. I really don't want to use an adapter. And I would rather not have to replace that 5/16 line. But over all, I don't want to create a problem trying to solve one...

So, has anyone here put a 5/16 line on a -6 fitting without any issues?

The line in question in the picture is the fitting touching the line.

That black and red fitting goes to the stock hard line. I would love to connect the FMU line directly to it. Basically cut off the stock type fitting from the FMU line and connect it to the -6 fitting.