did you check to see if it went into protection mode at the time? since you have time, you should just replace that 30a back to the original 40a.

you say the amp is on the floor, but is it under the seat? or sitting wide in the open. i remember going for a 1.5 hour drive in 90+ degree weather bumping the system hard the whole way. at the end of the drive, the amp was so hot, i couldnt keep my hand on there for more than a couple seconds. but it never went into protection mode.

keeping the amp on the floor is fine in terms of keeping it cool, but just make sure it gets some air and is able to dissapate the heat easily.