You know the issues with weight and also, I assume, with power. If I were flying an Epic on my old Flyer rig I would probably try to get the camera configured with a handgrip and a boatload of those "20 minute" handgrip batteries. Or maybe the camera will be configured with an AB plate so you can fly a dionic on the back, which adds a couple of pounds but I think would be do-able. What you want to do is power the camera separately from the rig, so you are only running the follow focus and monitor off of the rig.
You can buy a bracket from Tiffen to mount 15mm rods to the front of your Flyer plate (the holes are there), or if you have a drill press and a Redrock Micro (or similar) 15mm rod clamp,
you can drill and tap new holes through the clamp to mount it to your plate (the existing mounting holes in the Redrock bracket don't line up).
Or there are some Epic baseplates that accommodate 15mm rods. Don't get talked into a 19mm Arri-style dovetail. Too heavy for Flyer.
Now you have a mount point for your motor. BFD should come with a rods bracket. Of course, you'll need a BFD power cable for the 2-pin Flyer power lemo. You'll have to get one made; no one is likely to have one. Make sure you get an extra-long one, since the Flyer's power connector is in the rear of the camera stage.
Another possibility might be to simply velcro the receiver to the side of the camera.
My overall advices is that you MUST INSIST on a prep, at least a couple of days ahead of time, with the exact camera configuration (all the bits and pieces) that will be available on shoot day. Otherwise there are at least 75 different ways to be hosed, especially in the Red world, where there is so little standardization of accessories and everybody has a different kit.
Hope that helps.