Squirrelled. It doesn't work in standard British English, I know, but most North Americans pronounce the word as a monosyllable..."squirld", in effect...as in "He had squirrelled away money in lots of accounts."
screeched (and its variants) ,scratched, stretched, scrunched all have 9 letters.
I've yet to equal the 10-letter 'scraunched'......but it's not in Chambers