Without resorting to (read as: figuring out) a program to determine all the possible and best answers, here is what I've come up with for words longer than six letters:
amasses masses masse mass ass as a (though the E should have an accent in masse...)
mangled mangle mange mane man an a
sharped shared shard hard had ad a
mangled mangle mange mane man an a
sharped shared shard hard had ad a
EIGHT!
prattled rattled ratted rated rate rat at a
startled started stated state stat tat at a
prattled rattled ratted rated rate rat at a
startled started stated state stat tat at a
Forget EIGHT, move on to NINE!
spiriting spirting spiting siting sting sing sin in i
(spirting is antiquated, so 8 and 9 could be splitting and spitting)
spiriting spirting spiting siting sting sing sin in i
(spirting is antiquated, so 8 and 9 could be splitting and spitting)