Hey! I love this tail! Was wondering what the trick is to getting the fabric on the foam frame, both measuring it correctly and actually putting it on the frame. I'm working on a tail like this only a bit shorter, and can't figure out how to stuff around the foam and use the frame!

You do the equivalent of a duct tape dummy for the tail. I wrap it in paper towels or plastic wrap to give the shape and act as a backing, then duct tape it over for a fabric pattern. Then I sew the main length-wise seam(s) of the tail while leaving enough of a hole around the base end to slip it over the frame. I leave it inside-out initially and roll it up over the spine from the tip up. You can use a few dabs of hot glue to secure the fabric to the tail tip and any of the foam sections as needed, but don't overdo it or you'll lose of the fabric stretch (and thus tail flexibility).
From there it's a mix of machine & hand sewing to close off the seams around the base of the tail and secure the straps (though I do rivet the straps to the base's T-joint before I do fabric). I do my airbrushing and scales last, once the spine and fabric are secure. I've also found that for the tail you don't need much if any seam allowance if you're using stretchy fabric. I typically use a cotton-lycra or polyester-lycra blend with 50% to 70% 4-way stretch. Fabric.com has a pretty good selection, and you can always dye and/or airbrush as needed if you can't find the exact color you need.

Wow thank you! Thats incredibly helpful! Duct tape dummying didn't even come to mind. I luckily have the fur and materials I need, just needed someone with the experience to give me tips!

Hey, no problem. Fursuits can get tricky, and every one I've done so far has been a learning experience (I'm working on my 5th atm). Online tutorials and advice can be huge help, but in the end it all boils down to trial-and-error and seeing what works for your own style.