I can confirm that NCK Dongle can flash Fierce.I Flashed to my Fierce 3 different firmwares (TMobile,Metro,Multilanguage) and everything works.The worst was the multilanguage FW-every click spend to much time,looks unresponsive but after 5-10sec it does what I want to do 
Have no these problems with Metro or L2HUMH2 TMob firmware.
Have no these problems with Metro or L2HUMH2 TMob firmware.