Losi 8Te - Diff Oil Weights?

Yeah, my current 7/7/3 is feeling great round 180 corners as it really turns well but also when I need some punch then it feels a little lacking and also seems to lack a little drive down the straights. To be fair the oil is about 6 months old inside the diffs too which means they are bound to have broken down to a lighter grade equivalent.

I'll try refreshing them with 7/10/3 and see how that feels.

I have a front Smartdiff for the 8T, I'm guessing by putting the spur gear onto it then it could also be used in the centre? Would that work? Any recommendations on the best springs to use in it for racing a 8T 1.0 BL?