Those add on fuses are tiny, usually 2 or 3 Amp PTCs. We did some testing with bigger PTCs in one of pdibs threads, but I halted work on it until Rob brings the sub ohm kit, because the game will then change again and we'll need different denominations of fuses.
The project will start again once I got my paws on the kit =)
Until then you can use the add on fuses, just coil accordingly.