What kind of gauge do you ahev and how many fill-levels can it display? The number of probes is related to the number of unique levels your gauge can display. Four usually relates to E, 1/4, 1/2, 3/4, F (empty + 4 additional states). 6 probes would probably give more detail between Empty and Full.
I would order more probes.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC