I've used GSO for a long time and never had anybody have an allergic reaction. Seems to be "thinner" than cottonseed oil (which I used to use)... and a lot of my stuff is high mg/ml.
arachis oil is a horrible idea. if somebody has a peanut allergy, arachis can put them into shock and that's bad news for them and me.
arachi is what the pharm companys use not UgL's remember you have to sterilize your oil. You can also use safflower oil. grapeseed is thinnner your right that is why most UGL's just use it for high concentration products -in example a Test 400 or Test 500.