These switches were designed for HSS Strats with a non-splitable humbucker in the bridge.

In all of these switches, notch #3 (mid in SERIES with neck), connects the middle and neck pickups in series, just as the two coils of a humbucker are wired.
This tone is very much like having a "front humbucker" in the guitar. With the 5-way at throw #4 (bridge+middle), this notch will simulate a two-humbucker guitar with its toggle in the middle (both pickups) throw. How close this simulation comes to the "real thing" depends on your pickups.

FAT-HSS (c) TONE CHART
NOTCH NAME
(tone knob)
Normal
(10)
Neck on with Bridge
(9)
Mid SERIES with Neck
(8)
5-way (down)      
(1) neck
n
n
n
(2) neck + middle
m+n
m+n
n
(3) middle
m
m
M*N
(4) bridge + middle
b+m
B+M+N
B+(M*N)
(5) bridge
b
B+N
b


Memphis HSS (c) TONE CHART
NOTCH NAME
(tone knob)
Normal
(10)
Neck on with Bridge
(9)
Mid SERIES with Neck
(8)
Neck SERIES with Bridge
(7)
5-way (down)        
(1) neck
n
n
n
N*B
(2) neck + middle
n+m
n+m
n
(N*B)+M
(3) middle
m
m
M*N
m
(4) bridge + middle
b+m
B+M+N
B+(M*N)
b+m
(5) bridge
b
B+N
b
b


FAT-O-Caster V.4 (c) TONE CHART
NOTCH NAME
(tone knob)
Normal
(10)
Neck on with Bridge
(9)
Mid SERIES with Neck
(8)
Neck SERIES/out of phase
with Bridge (7)
5-way (down)        
(1) neck
n
n
n
-N*B
(2) neck + middle
n+m
n+m
n
(-N*B)+M
(3) middle
m
m
M*N
m
(4) bridge + middle
b+m
B+M+N
B+(M*N)
b+m
(5) bridge
b
B+N
b
b


FAT-O-Caster V.5 (c) TONE CHART
NOTCH NAME
(tone knob)
Normal 
(10)
Neck on with Bridge
(9)
Mid SERIES with Neck
(8)
Mid SERIES/out of phase
with Neck (7)
5-way (down)        
(1) neck
n
n
n
n
(2) neck + middle
n+m
n+m
n
n
(3) middle
m
m
M*N
-M*N
(4) bridge + middle
b+m
B+M+N
B+(M*N)
B+(-M*N)
(5) bridge
b
B+N
b
b


The FAT-O-Caster (c) changes the way the pickups are wired into the circuit.
The NAMES of the NOTCHES describe HOW the pickups are wired...

KEY:
+   = wired parallel
*  = wired in series
-B = Bridge wired out of phase
lower case letters = "stock" strat tones
UPPER CASE BOLD  = new FAT-O-Caster tones