Yeah the 42" is very thick bezel at the back good spotting, its taking up pretty much the entire back base.
see here its more clearer:
But the 48" which is few inches bigger totally different see here:
The mainboard and ps are all placed at the bottom half tv casing almost.
Its a bit of a curious design really, could the electronics really take up all that space?
One thing I spotted is the LG C2 42" has all 4 hdmi ports and all the ports on the side which is far better then the C2 48" which has 1 hdmi port on the back and some other ports also which is a pitta if you are wall mounting or pushing the screen back against the wall which naturally TV manufacturers don't do
Maybe this was why they had to arrange the mainboard and p/s to take up all the space of the 42" back casing.