The /æ/ vowel is spelled <a> followed by two consonants or by one consonant in a monosyllable, apart from <ai> in plaid. The /aʊ/ diphthong is spelled <ou> or <ow>, with one exception <ao> in the word Maori.
This contrast is between a short vowel and a diphthong with the sounds well separated in the mouth, so it should not cause any problems.
There is one pair involving a taboo word: shat/shout.
Interesting pairs include:
The density value is 5.52%. The pairs make 58 semantic contrasts, giving a loading of 49.1%.
Al owl at out attar outer bad bowed band bound banded bounded banding bounding bands bounds banned bound bat bout bats bouts bran brown brand browned cad cowed cancel council cancel councils cancel counsel cancelling counselling cancelled counselled cancels counsels cant count canted counted canting counting cants counts canter counter cantered countered cantering countering canters counters carry cowrie carries cowries catch couch catches couches catching couching Chas chows clad cloud clan clown clans clowns clannish clownish daddy dowdy Dan Down Danny downy drat drought drats droughts expand expound expanded expounded expanding expounding expands expounds fanned found flat flout flats flouts Fran frown GATT gout gnat knout gnats knouts grand ground Hal howl hand hound handed hounded handing hounding hands hounds has house lad loud ladder louder lass louse lat lout manned mound marry Maori marries Maoris mass mouse massed moused masses mouses massing mousing massy mousy massier mousier massiest mousiest Nat knout panda pounder pandas pounders pander pounder panders pounders panned pound pat pout patted pouted patting pouting pats pouts patch pouch patched pouched patches pouches patching pouching plaid ploughed rand round rands rounds rat rout rats routs ratted routed ratting routing recant recount recanted recounted recanting recounting recants recounts sand sound sanded sounded sanding sounding sands sounds scat scout shat shout spat spout spats spouts spatted spouted spatting spouting sprat sprout sprats sprouts tan town tans towns tat tout tats touts tatted touted tatting touting
John Higgins, Shaftesbury, November 2009