Got a bargain today on lots of wood to build a workbench with. However its that planed rounded edge stuff so by the time I finish planing all of the round edges out the top will be quite thin. I do have enough wood to make what I’ve shown in the attachment, but is this a good idea? In terms of wood movement and whatnot. All the grain is running in the same direction just the piece is turned 90 degrees.
You should be fine after scrubbing off the rounds, unless the rounds are really bad. You should still have a little more than 3″ after you plane it flat and take out any inevitable twisting. Also remember that you have to plane some of the roughness out of the faces of the stock to give a good glue edge, which will also reduce the amount of the rounds you have to take off the edges.
The issue that you might well face is that you need to allow for the wood to move, which it can when there is only one layer. I wouldn’t recommend having two glued together layers for the long term, as you may find you have issues a year or two down the line.
I work alongside Paul to plan and produce the videos for Woodworking Masterclasses