I DD a 15lbs flywheel, I'll have to check in the records who made it, but even though it was a learning curve I don't see myself going back from it. 8.5? Sounds a little extreme for DD purposes, the neutral chatter as is is already quite obnoxious, but imo it adds character :P
Interested to see which you go with, always good to remember this stuff for the next time mine needs to be replaced(knock on wood)