I managed to make it to Course 5 Mobility Gel test 2.
There were only 2 or 3 times I had to lay the controllers side by side, or one on top of the other to move both robots at once.
One time I had to hit a trigger with my mouth, but so far I'm surprised at how easy it is to do this once you figure out the puzzle.

You do know there are dudes willing to play with you on the internetz 

How does one... go about co-oping alone ? 
 
I read your post but still.. duder. woah!

You are crazy 
Also, I did that once for an achievement 

I'm sorry.

I beat it with a dance mat.

By playing it alone you're missing out on a wonderful experience made up of frustration, grief and ultimate satisfaction with another duder.

This is like that guy who beats games on a dance pad, only more sad. 

I played it with my girlfriend's 3 year old brother, that's all the handicap I'm ever going to deal with.

I tried online co-op once, and I made this kid (who was at least 20 years younger than me) flip out and eventually quit.
I'm pretty slow to figure out the puzzles, so I'd probably just make more people angry.
I'll need to at some point for the achievements, especially the time one but I'm waiting until it's absolutely necessary.

only enough to get a couple easy cheevs. 

I'm sorry.

:(

By playing it alone you're missing out on a wonderful experience made up of frustration, grief and ultimate satisfaction with another duder.

I finally beat co-op by myself, it is possible.
5-9 had a part where I thought I was going to need another person, but I was able to setup my other player to minimize dual controlling.