Fastlane parts;

[RC-Monster Mike]

The 1/8 diffs are not much heavier at all vs. the alunimum cased and cupped diff. That is a heavy Savage! The GA 7075 bulks are as you described (heavy, but strong!). When using the diff cups and aluminum cases, I have only seen (or heard of) the spiders stripping a couple times (once by myself). In both cases, the diffs were in pretty worn out condition and had quite a bit of slop (needed shims badly - the ones I stripped had close to a year of use before they let go). The stock maxx spiders are very strong when they are shimmed properly. Inside an aluminum case, I haven't heard of stripped ring/pinion gears at all (not saying it hasn't happened, but I haven't witnessed it).
I find it a little ironic (funny) that you mentioned lightweight and 16 cells in a description of the same vehicle. :)
Your BL savage looks pretty sweet in the pictures you sent. Do you mind if I post them in the gallery? (or could you post them in the gallery?).