5 letter words:
spiff13,
stiff11,
tiffs11,
4 letter words:
pfft12,
tiff10,
fist7,
fits7,
sift7,
pits6,
spit6,
tips6,
3 letter words:
iff9,
fit6,
ifs6,
pis5,
pit5,
psi5,
pst5,
sip5,
tip5,
its3,
sit3,
tis3,
2 letter words:
if5,
pi4,
is2,
it2,
si2,
ti2,