I released Ultima SDK dll with UOP support (including source code). It has compatibility with UOFiddler, just overwrite fiddler's ultima.dll and change art.mul, gumpart.mul, sound.mul paths to uop files. Artidx.mul, soundidx.mul, gumpidx.mul should be blank. After doing this, restart Fiddler and it will read items/land tiles/maps/gumps/sounds from new uop files directly. The code is included with my copyrights ;) Have a fun.