Resizing and/or laying out the bar in the opposite direction is not difficult. Just examine the base and work from there. If you want it a foot longer or shorter, just add or subtract a foot from the length related base parts. Pages 11, 12 and 13 are most helpful.
To modify the Side Leg (B section), you would add or subtract to base parts 9,11 and 13.
To modify the Main Leg, add or subtract from parts 1, 2, 3 and 7.
Once the base is resized, add the vertical parts.
Next, for the side leg, you would add or subtract the same amount as the bottom for parts 26, 30 and 32.
For the main leg, add or subtract the same as your base changes for part 31.
At this point you have a fully modified core framework from which all other remaining parts can be referenced.
It seriously requires no more than third grade math skills.