The /æ/ vowel is spelled <a> followed by two consonants or by one consonant in a monosyllable. The /ʊə/ diphthong is spelled <our> or <ur> in lured.
This contrast is between a short vowel and a diphthong well separated in the mouth, so it should cause no problems.
The density value is low at 0.85%. The pairs make 7 semantic contrasts, giving a high loading of 78.8%, not significant with such a short list.
bass bourse dally dourly gad gourd gads gourds harry houri harries houris lad lured mad moored pally poorly
John Higgins, Shaftesbury, November 2009