Highest dose i have ever taken was 1900mg it was wonderfull but not as intense or long as the 4th plateau trip i had on 1300mg without tolerance.
At the risk of having this turn into one of "those" threads... My highest was 888 mg DXM polistirex on two separate occasions. The first tore me away from everything so severely that I felt I was becoming nonexistent and/or brain dead. Not pleasant, and no real visuals to show for it. The second time resulted in a week-long trip sparked by a really bad peak due to less-than-ideal circumstances at the time. (It's best to always be on the same page as those you may be tripping with.)
Anyway, what I was getting to (in relation to an ongoing topic) is that higher doses don't always guarantee visuals. And that low doses can sometimes be surprising, even for seasoned trippers.
Visuals on DXM, I think, are attained by "tuning in" to a certain frequency, or layer of consciousness. It's like having this virtual scratch pad I can sketch on. The more I get used to using it, the more I'm liable to see what I'm building as an actual visual, and the more elaborate the structures I'm able to build.
It has now gotten to the point where it's like I'm running the best physics and graphics software on the best supercomputer, with real-time control over complex content, and with a heavy dash of creativity thrown in. The good (detailed) visuals still aren't very bright, much like looking at a sharp, printed image from a printer that is running out of ink
All in all, DXM's visuals are very astonishing. I think people who are doubtful of just how powerful the human mind is should try to reach such a level, with DXM or without.