Another update to this old thread.
Been having the same issues so did some testing. The amyl acetate seems to have no effect on keeping the castor in solution. I mixed up to 5% of it in my 70% fuel and with or without it the fuel started to cloud up at exactly 25*C (77F), that was with Blendzall castor. Warm it above that temp and it cleared right up.
I mixed some fuel with Sig AA castor and it stayed clear to 22C (72F). I'm not positive if the brand of oil is the difference, it might be the length of time sitting around that has something to do with it. The Blendzall fuel was six months old while the Sig was mixed fresh.