MusicNutter I personally would have David Robertson as the PAN
First thing to think about is the amount of work implied before you get such a project underway. Bear in mind that, if you create new artists "David Robertson" and "Chimp", all entries listed under "David "Chimp" Robertson" will need to be moved subsequently to one of those PAN you may possibly set up. This may turn out to be a rather tough job.
Likely you still want to give it a go, so it's about time now to pick "your" David Robertson from the pool. If you need to, go ahead and create "David Robertson (11)". Once you're done with moving all these entries you may consider linking both "Chimp" and "David Robertson (x)". This is done by adding one of them to the alias field on the artist page of the other.