The /u/ vowel is spelled <oo>, <ew>, <ue> and <o> in who, and occurs in the letter name U. The /eə/ diphthong is spelled <areCe>, <air> and <ear> in bear.
There is one taboo word pair: coon/cairn.
One interesting pair is hoodoo/hairdo.
This is a contrast between a long vowel and a diphthong, widely separated in starting position and distinguished by lip-rounding. It is not a problem for any learners.
The density figure is 6.86%. The set makes 40 semantic contrasts giving a loading of 60.6%.
blew blare blue blare blued blared blues blares boo bare booed bared boos bares boo bear boos bears boon bairn boons bairns booze bares booze bears chew chair chewed chaired chews chairs coo care cooed cared coos cares coon cairn coons cairns do dare do's dares flew flair flew flare flue flair flues flairs flue flare flues flares food fared glue glare glued glared glues glares hoodoo hairdo hoodoos hairdos lieu lair loo lair loos lairs moo mare moos mares noon Nairn ooze airs shoe share shoes shares shoo share shooed shared shoos shares snood snared snooze snares too tare two tare twos tares U yeah who hair who's hairs whose hairs who hare who's hares whose hares who'd hared woo ware wooed wared woos wares woo wear woos wears you yeah