Since the FUL algorithm creates spectra which contain all peak-peak conincidences, there is a smooth component to the background subtracked spectrum. This smooth component is made up of both compton and unresolved photopeaks (continuum) events. Since levit8r assumes no such background exists when it produces the calculated spectrum, levit8r_ful also allows for the removal of this smooth component.
To choose the background subtraction method of interest, the command FU has been added to levit8r_ful and levit8r_gls_ful. When you start the program, the default is FUL subtraction, FUL_RANGE = 10, removal of smooth component is turned on. Giving the command FU chooses levit8r default subtraction. Giving FU 10, for example would choose the FUL background subtraction with a FUL_RANGE of 10. When FUL is chosen, the program also asks if you wish to subtract the smooth component as well.
Currently, these programs do not apply FUL with you use the commands FTI, FTE and FTB, i.e. you are fitting the level scheme to the cube. However, in GLS the FUL algorithm is used with the SB (search band) command.