getting cage bends all on one plane

Here's what I do (but I'm eager to see how others do it better):

Take an L bracket and hose clamp or take a short piece of flat metal and tack weld it on the end of your tube-- the last part that would go into the bender if you went that far. Check it with a level before bend #1 but while you've put some tension on the bending lever.

After you complete bend #1, check to see where the bubble falls again.-- usually I tweek the bracket again because I know the bender "settled" from me pushing/twisting on it while bending, but I take note of the difference.

When you position the tube for bend #2, put some tension on it again (support however you need with a chair back or step ladder or whatever) while you maneuver around and set the level mark again to how it was when you were finished with bend #1 or possibly a smidge toward where it was before you did bend #1 but not all the way to the pre-bend 1 location.

Go ahead and start bend 2 (where it is supposedly even with the first bend) and do a degree or two so it sorta "sticks" without the tube sagging. Then go back and check the level. You can often times adjust if you need to a tiny bit if you need to.

I do get better results when I have a helper holding the other end of the tube, but there have been times when the "helper" is lifting too much and throwing off the level mark.

Spank's description is exactly how I do it (small wonder, he taught me), and I get perfect results every time.
When I lay the bent part (main hoop or halo) on the concrete patio, it is flat, with no gaps between the tube
and the patio.

Having a helper is almost essential, however.   You will need them to hold the already-bent section while
you are looking at the level or tightening the clamp on the bender.   Also, having them call out the numbers
on the degree pointer makes it easy to sneak up on the proper angle, allowing for spring-back.

A feed roller on an adjustable-height stand (like woodworkers use) is ideal for supporting the un-bent
portion, but a sawhorse will also work.

I just use a piece of string tied to one end of the tube. Draw it across so it lies on top of the tube on both sides of the mandrel. You can then just eyeball it. It's triangulated if the string is level with the top of the mandrel. No level required.

Maybe if you worked on your people skills making friends would be easier?

(ducking)

http://rs897.pbsrc.com/albums/ac180/Ran … g~320x480/

I use clamp-on bracket and a magnetic base digital level to manage tube rotation during bending.  Keep the angle constant for in plane bends.  You can see the red clamp on bracket in these photos.  I think I paid about $25 for that widget but you can easily make one yourself.