Sounds like you could have aura! A phenomenon mostly connectedto migraine sufferers. I also have cluster with aura, the aura came upon me in the last 5 years of my 20 years of cluster!
Hey Big J... in my experience, insurance companies are much more focused on "units" (not MGs) allowed per month. Try to get a script for the 6mg (.5ml) auto-injectors and see if your insurance will allow 10 cartridges/month (giving you twice the total MGs of sumatriptan).
Or, just get the vials... waaaay better.