Vowels 9 and 12, /u/ versus /ə/ 15 pairs [cuckoo.html]
Since the schwa has to be unstressed while /u/ is likely to be prominent, very few pairs were found in the dictionary. I have included several involving the weak forms but, cos, from, to, was and you which are of doubtful status since they cannot occur in isolation.
The density figure is 0.32%. The set makes 11 semantic contrasts for a loading of 73%.
babu barber
babus barbers
bayou buyer
bayous buyers
boot but
coos cos
cuckoo cooker
cuckoos cookers
Frome from
seafood Seaford
two to
too to
whom h'm
woos was
yew you
John Higgins, Shaftesbury, December 2009