steve i have had 4 enstrom pistons never had a problem with ring gear or delamination. i have heard of people having problems with delamination but these were on 1976 /1980s ships. the rotor blades are lifed on condition when they start to delaminate they usually are very old .
they are not any worse that others read posts about koala vibration..
i know of a md600/900 both having probs with blades even robbos had to change there blades on 44s a few years ago
go try a enstrom its the only way but beware when youve done a auto in one robbos seem a bit [lot] fast and your check book might be coming out
regards steve