(Top photo courtesy of TFW2005.COM's Autobot Whirl Gallery; bottom photo courtesy of Starscream Gaga and the Generations Autobot Whirl Feedback thread. ~Superquad7)​

For Generations Whirl, this is how I modified mine to give him two (2) different leg options that both stand perfectly in just about any pose.

Just chop off the long black feet, right above the screws nearest to the bottom. Then you can turn the legs and he will stand great, whether legs out straight or knees bent for more dramatic poses. It also seemed to make robot mode with the intended chicken legs stand better in more poses too. I personally cut my toes at angles so they work well either way rather than at the original slant it had for flat footed standing in chicken leg mode:

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I don't dislike the chicken leg look, but I wanted the option of more normal bot legs without him having to stand weird all the time.

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How you do the cut depends on preference really. Some may want to cut them at an angle so the toes sit flush with the ground in alt-legs version. I cut mine in a way I thought worked best for using either option, since I like both.

I'm adding new pics of helicopter mode now to show exactly where I cut the toes on mine. Using a Dremel cutter disk, small fine blade hand saw, or laser katana, it should be easy to replicate what I did using these pics for reference.

Not much. You just couldn't really stand him right with the legs backward until cutting the black toes shorter, so this makes the other leg option work better.

Another option is to cut off the two small raised back knee armor pieces (the ones that form front knee armor in my alternate legs mode) on both legs and then you can simply bend the knees like humanoid legs without turning them around or needing to cut the toes. Neither modification will hurt the helicopter mode. I just wanted to have the other feet option, too.