I am also planning to fill mine, so that I can use the Devil-Horn emblem from one of the group buys.
I am looking to use the same stuff, but from what I understand when you purchase the stuff, it comes in a large quantity. You will have lots leftover. You can use a plastic welder, or a standard soldering iron to "weld" the FirberFlex in. You can then use a glazing putty or other stuff for finishing it up.
I think KeithH sold all of his remaining stuff, but I'd want to see how it has held up. I haven't searched for it, but I believe you need the right plastic rod for the material that makes up that nose piece (polyurethane?).
If anyone wants to split/share some of the cost/material, I am in for buying some (enough to get mine done).