Vowel /ɪ/ is generally spelled <i>, <y> or <ie>. The /ɪə/ diphthong is <ia>, <ea>, <eer>, <ear> or <ier>.
The original search produced a great many extra pairs in which the /ɪə/ was not a diphthong but was two syllables, such as airy/area or collie/collier. These were discarded since they really belong in the schwa versus null column, being made by adding the schwa to /ɪ/.
The only pairs with taboo words are piss/pierce and quiz/queers.
The mean density is very low at 0.1%. The list makes 19 semantic contrast, giving a high loading of 79%.
bid beard bidding bearding bids beards biz beers chid cheered cirrus serous fizz fears his hears is ears lid leered Liz leers Millie merely Ms meres piss pierce pissed pierced pisses pierces pissing piercing quid queered quiz queers rid reared rill real Sid seared viz veers whiz weirs
Credit: John Higgins