Bells isn't the kind of wave where I'd worry about hitting the reef. I've not surfed it but I've been past when It was semi working and the wave looks like it's breaking in deep water, and I've never heard anyone talking about how gnarly the reef is. Also Bells is not a good bodyboard wave, it's too fat for that.
It's not like an Indo coral reef. First time I surfed over coral I was nervous but found that It took some effort to hit the reef and when I did I made sure I touched down with my booties.
Don't ride a wave too far if you are worried about the shallow inside section, and stretch your arms and legs out and float like a starfish if you come off in the shallows, then again you are on a BB so you won't fall so you don't have to worry half as much.
The real shallow reefs I have surfed were rock shelfs so hitting that didn't shred me. The places where you are likely to hit reef are where the waves are hollow (breaking from top to bottom) otherwise wipe outs are more like a beach break, and how often do you hit the sand hard on beach breaks? Probably not very often.....
Oh and often the bigger the waves, the deeper the water so big can sometimes be better if you are scared
