how much RPM have you lost at the stripe or any at all with the slip? Interesting the shift drop RPM has not changed, with the slip I would think oyu are blowing through the converter or you just do not have enough rear gear..

That's not alot of rear gear for sure, I would be leery of having it there for such an engine. With a 655ish deal likely be not as big of a concern. At least on our 655 that dont seem to care so much where its shifted