9sp/10sp compatibility in Shimano SLX drivetrains This is related to my previous question about SLX chainrings.
I'm half way through upgrading my drivetrain from 2x9 to 2x10.  I currently have:

Shifters: SL-M670-I (10sp),
Chainset: FC-M665 (9sp double with bashguard),
Rear mech: RD-M675-GS (10sp),
Front mech: an old Deore 3x9 that doesn't play well with the other parts and needs replacing.

I'm trying to make this drivetrain work at as little cost as possible, and I have two concerns:

I understand that, officially, the M665 chainset isn't 10sp-compatible, but people have reported (in this thread and on Bikeradar) that it works fine.  Are there any complications in this?

I shouldn't use the newer FD-M675 front mech because the chainline doesn't match that of the chainset I have (48.8mm and 46.8mm respectively).  That leaves me with the FD-M665 front mech, but will this be compatible with my shifters?



Edit: This thread suggests that the 9sp front mech will work with the newer 10sp shifters.  Can anyone confirm or provide more information?

In response to PeteH's comment: In short, what I don't understand is:

Why exactly should the M665 chainset not be 10sp-compatible, while the M660 is?  Are the chainrings too wide, and if so, why do people report that it works anyway?

Do the 665 and 675 front shifters have different cable pulls?  If not, is there any other reason I've missed why the front mech from one groupset might not be compatible with the shifter from the other?
Unfortunately, the cable pull ratios are elusive and seem to be unpublished.
The difference in chain width between 9s and 10s is less than 1mm so it won't make much of a difference once the mech is adjusted correctly. I have M660 on my bike and M665 on brother's bike and they aren't so much different, so if 10s is proven to work on one, it should work on the other.
Front shifters have the same cable pull, but front derailleurs have different travel rate between 9s and 10s. Therefore if you want to use a 10s shifter with a 9s crank it's actually better to use a 9s derailleur. Although both would work, a 9s would be more accurate in this case.