Great to see my favorite thread come to life again with all the M06 experts!
Too bad, that you´re not allowed to use fluid gear diff. It´s a shame, that Tamiya doesn´t bring one for the M05/06. I only run the 3Racing one in my M05L and my M06L, despite a modded Spec R in my M03.
They are nearly maintenance free, I open it once a year for a check and little cleaning. The advantage for me is the characteristics, as you can still have some diff action, when turning slow, like when you need the diff action on the axle to help for turn in. But when trying to spin it faster, the fluid locks and prevents spin out of the inner wheel.
I raced 2014 against a M06R Alfa on sweep slicks, the guy was damn fast and afterwards he told me to rum 7k oil in rear! Never thought that this could work in RWD. When he bought the car from an Nitro driver, it had even 10k oil in the diff...
I run 3k at the moment, which is great on carpet. With ABS and the brake turned slightly down, you can even brake into tight corners to reduce turning circle in some corners, where the M06 has a little push. And acceleration is great, too.
O.k., but you´re stuck to TCS rules, so I stop talking about diffs!
Which tires do you have to use in TCS?
And when using the BB shocks on the M06, make sure to have in rear enough shock length (2mm more) by the special M06 piston rod, when using the outer lower damper mount in the axle pin from the Pro kit.
And when doing so, I´d increase the piston hole to 1,3mm 3 holes like in the R-Kit. I do it vice versa also on my M05 Pro V2 on the front axle and liked it very much this racing season.

Have fun with the build, and give the project a little patience, when the first races may not be as good as expected.