u should ground whatever needs it where the wires are sketchy, u did a good job of doing the negative battery cable, u can do the positive battery cable to the starter which is pretty much the biggest connection point where u need the most power but, if should already have at least a 6 guage wire there, example, i rigged up my own stereo and when i did i just wrapped the ground wire around one of the bolts that another ground wire was on, without using any type of connector or nething, like that would benefit by doing it right, as for most connections on the car honda does a good job of setting up the electronics, thicker ground and power wires are typically for show or bigger amps in the back of ur car that need alot of power. in older cars it is suggested that you use a slightly higher cca (cold cranking amp) battery to get all the amps to whatever might need it since some wiring may be old and a little worn out. nice car CivicDXR even with the stock engine it looks very nice.