I added a small piezo buzzer and a light on the dash, in addition to the automatic float.
(I also added another pump, 1250 Attwood) When my exhaust developed a hole while underway, and the back started filling up with water, the light and buzzer came on, and I knew something wasn't right. The Pump was on for about 10 seconds, and then went off, so I knew it was keeping up with the flow, so I floored it to the ramp before checking it out (Not sure how wise this was)
I was sure happy I had added pump capacity and the warnings to be informed of what's going on.
The smaller your bilge, the FASTER you will sink with a similar diameter hole, all else being equal...small bilge = BIG pumping needs. Auto VERY important in my book too.