Micro stuff
humboldtblazer
The GH front ball-diffs are great, I use them on two of my three Micros.
One uses the "older" GH ball-diff and the second uses the adjustable GH ball-diff II.
The GH front diffs take their sweet time running in, it takes lots of mileage before they smooth themselves out.
On the rear diff side, stick with the HPI and fit a Losi Thrust Bearing: Losi Part #3098 in place of the bearing in the rear right/diff side wheel. This makes the rear diff a lot more adjustable and improves the rear end behaviour by losing that pain in the ass problem of always re-adjusting the rear diff..
Regarding the battery rubbing the belt, raise the battery pack a little by using an extra layer of double sided tape. I don't suffer from this symptom, as I use battery mounting plates for my (Penguin P3500 Series) chassis.
If you're using Velcro, the same applies, stick some double sided tape between the pack and Velcro.
Here's a pic showing my battery mount with Velcro, it should give you a rough idea on just how much clearance is needed