I would suggest to cut is insitio, when putting it on, this was you can press the fabric into the base coat preventing the end from comming out

I would cut the fibre while pressing it onto the base coat,the image was only a demo how to overlap
you can do multiple sections, does not have to be one piece, that may be better because you cube is quiet small

how did you get on with the cube

if you make 3 carbon pieces,
1 long one to cover the shorter sides with one long 1" wide strip in one go with opverlapping the corners and and then later cover the top and bottom 6"x3 1/2" sides
sometimes I use cling film to hold the overlapping corners down by wrapping it on top of the fibre

and you need a very sticky basecoat like the XRC basecoat, may get a small quantity on EC's website

A cube is significantly harder to wrap than a surfboard. All about the radius! 

I would actually suggest not trying to wrap around the corners, but rather try the technique demonstrated in EC's skinning tutorial (skip to 6:25):

https://youtu.be/aqwhcfQZT8U

To do that, I would cut 6 individual pieces of carbon that are each slightly larger than the sides of the cube, and stick them down to the base coat. When the base coat has hardened more, trim off most of the excess but leave a 2 or 3mm overhang as Paul demonstrates in the video, wet the carbon out with resin, and then once hardened you can sand the carbon back to the shape of the cube. That will give you a very nice neat seam on all of the radius that will be quite hard to spot, but avoid the problems you are having.

I like both of those ideas....I'm going to try both of them! Thanks guys