disconnect switch amp rating

In a few racing bodies, lke FIA rally, they are required wherever the battery is located. It is there to cut-off the battery in case of wreck/fire/etc. So, for racing safety considerations, it should be there regardless.

The heavier amperage rating is a good idea because if you do get into a wreck and the + cable is being pinched and shorted, you will have to break a lot of current; a lighter current cutoff may just arc over the contacts and weld itself closed with a shorted battery load in it. Besides the inconvenient fact that the 20A rating won't carry the battery currents you need in the first place.......!