How can I change registration number on Carenado aircraft?

Registration number can´t be changed in Carenado aircraft.
This is done to keep high quality standard in our textures, otherwise aircraft would have registration number with regular fonts.

You can change registration number modifying textures. 

Here is a forum with a video about painting our aircraft:

http://forum.avsim.net/topic/283391-carenado-repainting-tutorial/page__p__1778414__hl__repainting+tutorial__fromsearch__1#entry1778414