A friend of mine had a 1:10 solution of DXM
and guaifenesin and took 240 mg DXM and 2400 mg guaifenisin respectively - just the amount you're talking about.
He said the experience wasn't really horrible but cetrainly the worst time he had on DXM.
The nausea he usually only experiences while actually drinking the syrup was persistent during the whole trip. He had to lie down and stay motionless the whole time, and yet he still felt so sick it ruined the experience.
Around eight hours after taking the drug
, when the trip was pretty much over, he went to the kitchen to eat or drink. Despite his stomach being completely empty, the act of moving triggered a throw-up tic. He went around helpless, as the muscles in his throat repeatedly contracted until he lay down again.
Overall, it was not worth it, according to his words.
However, no one knows how your body is going to react. You might feel less nausea than my friend.
You might also turn up to be allergic to guaifenesin. Be sure to test it in advance by taking one pill, should you still decide to go for it.