5 letter words:
foist8,
obits7,
4 letter words:
fibs9,
fobs9,
fist7,
fits7,
sift7,
soft7,
bios6,
bits6,
bots6,
ibis6,
obis6,
obit6,
stob6,
3 letter words:
fib8,
fob8,
fit6,
ifs6,
oft6,
bio5,
bis5,
bit5,
bos5,
bot5,
obi5,
sib5,
sob5,
its3,
sit3,
sot3,
tis3,
2 letter words:
if5,
of5,
bi4,
bo4,
is2,
it2,
oi2,
os2,
si2,
so2,
ti2,
to2,