Thanks for the video, Terraphon.
I figured I'd add my findings for using this method on my 901...
I used a fiberfill called, "ploy-fil"made by a company named Fairfield (I'm pretty sure this is the same stuff Terraphon used)...
I tried to make my homemade filling about the same size as the original, but found it a bit harder to work with. By that, I mean harder to "shape" for fitting it in the cart, and stray filaments being much more prevalent. My fingers must not be nearly as nimble as Terraphon's because I had a hard time trying to fold those loose ends and get them to stay while I rolled the fiberfill. I found it easier to
lightly roll the fiberfill between the palm of my hand and the index and middle fingers of my other hand. I stress the term
lightly because, as it has already been said, you don't want the filling to be too compact or it won't wick properly.
The original filling was rolled into a cylinder shape and then folded in half. I did the same thing with my homemade filling.
Original filling (left to right; unrolled, rolled, rolled and folded)...
My filling (left to right; unrolled, rolled, rolled and folded)...
To remedy those stray filaments, I found two solutions that both worked well; cutting the excess with a scissors once loaded into the cart, or
quickly passing a flame across the end of the cart to melt them.
Just for the hell of it, I tried to make another filling that was more identical to the original. As you can notice from the pictures, the original filling in my carts was a bit more coarse than the fiberfill. The filaments are mostly aligned in one direction, and they are joined together at various points. I attempted to replicate that by holding the stretched out fiberfill, in a pair of tweezers, over the flame of a lighter. I made sure to keep the fiberfill about 6" (15 cm for you more civilized metric system users

) above the flame and continually moved the lighter around so as to not burn or over-melt the fiberfill. Given just the right amount of heat, the fiberfill filaments will melt slightly and bond with nearby filaments.
Here's the result (left to right; heated fiberfill and original filling)...
The melted fiberfill is much easier to work with. But, it remains to be seen if it wicks as well as the originals or my "plain" fiberfill fillings.
For right now, I'd say the original and the "plain" fiberfill fillings work about equal, with the melted fiberfill being not as good as the other two. I'll give them all some more testing and if I get different results, I'll be sure to post an update.