I run Mobile 1 Syn ATF (about 7.5wt) in my '00CR250 right now, but have tried others. I doubt you will have any problems with SS7, but I would be surprised if it cured the midstroke issue. From all I have experimented with and read here, this is a valving issue and no oil is going to make it go away.
In theory, I would think that a less viscous oil would have less tendancy to cavitate (foam).
If it's any concelation, the '01 is an improvement to the '00. :eek: