Splitting U(0,0,1)F
U(a,b,c)F = aU(1,0,0)F + bU(0,1,0)F + cU(0,0,1)F.
The first two of the three 'basic series' are both the primus, the first one in reverse.
The third one, U(0,0,1)F, is not part of the fabfour and it's not an operator, but being the basic non-zero-series, its split is all the more interesting.
The splitvalues show that U(0,0,1)2, which is the 'the series of triangular numbers', cannot be split secundus- or tertius-based.
U(0,0,1)FPrimus splitvaluesSecundus splitvaluesTertius splitvaluesQuartus splitvalues
[1]-11/(F-2)2/(F-2)0
[2]11/(F-2)F/(F-2)1
[3]0-2/(F-2)-2/(F-2)0
[4]1-F/(F-2)-2/(F-2)0

Splitting U(0,0,1)FPrimus
doubled
Quartus
doubled
Secundus
doubled
Tertius /(F-2)
doubled
Tertius
doubled
Secundus /(F-2)
doubled
Quartus
doubled
Primus
doubled
U-5F4+F3-2F2-F+1=-F*-F3-F2+2F+1+1=F2-2*(F3-F2-2F+1)/(F-2)+-F/(F-2)=F2-F-1*(F3-3F)/(F-2)+-2/(F-2)=-F2-F+1*-F2+1+0
U-4F3+F2-F=-F*-F2-F+1+0=F2-2*(F2-F-1)/(F-2)+-2/(F-2)=F2-F-1*(F2-2)/(F-2)+-2/(F-2)=-F2-F+1*-F+0
U-3F2+F=-1*-F2-F+1+1=F*(F2-F-1)/(F-2)+-F/(F-2)=F-1*(F2-2)/(F-2)+-2/(F-2)=-F-1*-F+0
U-2F+1=-1*-F-1+0=F*(F-1)/(F-2)+-2/(F-2)=F-1*F/(F-2)+-2/(F-2)=-F-1*-1+0
U-11=0*-F-1+1=2*(F-1)/(F-2)+-F/(F-2)=1*F/(F-2)+-2/(F-2)=-1*-1+0
U00=0*-1+0=2*1/(F-2)+-2/(F-2)=1*2/(F-2)+-2/(F-2)=-1*0+0
U10=1*-1+1=F*1/(F-2)+-F/(F-2)=1*2/(F-2)+-2/(F-2)=1*0+0
U21=1*1+0=F*1/(F-2)+-2/(F-2)=1*F/(F-2)+-2/(F-2)=1*1+0
U3F+1=F*1+1=F2-2*1/(F-2)+-F/(F-2)=F-1*F/(F-2)+-2/(F-2)=F+1*1+0
U4F2+F=F*F+1+0=F2-2*(F-1)/(F-2)+-2/(F-2)=F-1*(F2-2)/(F-2)+-2/(F-2)=F+1*F+0
U5F3+F2-F=F2-1*F+1+1=F3-3F*(F-1)/(F-2)+-F/(F-2)=F2-F-1*(F2-2)/(F-2)+-2/(F-2)=F2+F-1*F+0
U6F4+F3-2F2-F+1=F2-1*F2+F-1+0=F3-3F*(F2-F-1)/(F-2)+-2/(F-2)=F2-F-1*(F3-3F)/(F-2)+-2/(F-2)=F2+F-1*F2-1+0