I think I see what you are saying. You are looking at it as skewing from only one direction - which I guess it is. However, you should still get the same shape, just higher than you wanted since the "wrong" side is skewed. Adjusting the y position on your object to compensate should put it back in place with the same shape you want.
Now that could be an issue if you want it at the bottom edge of the screen, because there might not be enough room to adjust for the skew. Also if you are animating the value it'd be more tricky ( skew and move y to adjust ).
Optionally would flipping it ( horizontally? ) giving a mirror image give you that result? My geometry skills aren't up to snuff

Although that wouldn't be very useful assuming you might be putting a texture on it.
You might wanna take a look at this:
https://github.com/mickelson/attract/issues/70It's difficult to explain, perhaps you can do a quick paint job or something to mock out the desired shape you are going for?
edit: are we going for "coverflow" here?? considering you were also asking about the conveyor module
