My kit arrived this week along with the 2.4" RB6 rear wheels I had ordered. I was able to get the following offset measurements using a digital caliper where the Width was measured on outside wheel edge and Backspace was measured to the flat hex face which would press up against the face of the hex nut on the axle:
TLR (Rear) 2.2": (Width = 38.2mm) (Backspace = 26.6mm) (Offset = (W/2)-B = -7.5mm
RB6 (Rear) 2.4": (Width = 38.8mm) (Backspace = 26.7mm) (Offset = (W/2)-B = -7.3mm
If I understand this correctly, when using the RB6 2.4" wheels, they will add a combined 0.4mm extra track-width on the rear as opposed to using the stock TLR 2.2" wheels.
It's also worth noting that I'll also gain a combined 1.2mm of extra wheel width with the RB6 2.4" wheels which could potentially add more stability.
I also measured the front wheels too:
TLR (Front) 2.2": (Width = 24.6mm) (Backspace = 22.4mm) (Offset = (W/2)-B = -10.1mm
TLR (Front) 2.4": (Width = 25.6mm) (Backspace = 22.5mm) (Offset = (W/2)-B = -9.7mm
So on the front, it seems that the switch to 2.4" wheels will net a combined increase in 0.8mm of track width and 2.0mm extra wheel width.
It appears that switching between 2.2" to 2.4" wheels between front/rear may offer many different tuning options to consider with the varying offset/track-width changes. I would've expected the offsets to remain the same when going from 2.2" to 2.4"... go figure???