Shortening the length of a horizontally offset mesh

If I want to slightly shorten the length of the lower leg of this giant mecha robot, how can I do that without horribly distorting the mesh itself?

Doesn’t it have to be perfectly horizontal? Even if I select everything and try to rotate it 45* to be perfectly horizontal with the global x axis plane, it won’t align perfectly.

The two below images are screenshots demonstrating my problem.

Attachments



Use a custom transform orientation by using a face on the geometry as a reference. A good reference would be one of the big flat faces on top of the leg.

Enable custom orientation by first selecting the reference face or edge, then hit Ctrl + Alt + Space. When a custom orientation is in effect, it is shown as either “Face” or “Edge” in the orientation section of the toolbar. The 3d manipulator also changes axes.

To use the custom transformation while grabbing/scaling etc, double tap the axis keys.https://i.imgur.com/nAe3Mhv.gifv

Remember to change back to Global orientation afterwards.

https://i.imgur.com/nAe3Mhv.gif

Thank you!!!