Re: 鞋: haai4 or haai4*2? (e.g. 蛙鞋)

Checked syllables of both tone 8 and 9 have some characters that may also change to Tone 2. Here are some examples with coda p/t/k each:

Tone 8 (long vowel only) - 文件夾[gaap8*2], 牙刷[caat8*2], 麻雀[zoek8*2].
Tone 9 (long vowel) – 豉油碟[dip9*2], 娥眉月[jyut9*2], 約莫[mok9*2].
Tone 9 (short vowel) - 紙盒[hap9*2], 人日[jat9*2], 郵局[guk9*2].