Yeah, MP-11 starscream has the same hand so he can do it too:
I thought that was cool when I first heard of it. However, in person, it's not that great. Not only is Megatron comically oversized (which I don't mind so much considering he's meant to transform into a robot the same height as Starscream), but it's really Starscream's thumb doing all the holding, so you have to angle Megatron in to get the thumb deep enough into the groove to hold:
Personally, I prefer to display Megatron sitting on Starscream's shoulder. It's as if Megatron's ghost is representing the niggling self-doubt that causes Starscream to repeat his bumbling mistakes and prevents him from rising up to be the great Decepticon leader he can be.
Or, you can view it as a parrot Starscream had created after Megatron's death to mock his former leader and reinforce his contempt for Megatron. Which is probably more in line with the Starscream we actually got in the G1 series, rather than the Starscream I wanted him to be.
I don't constrain myself to any lines, though so far my collection has mostly been CHUG since I prefer the mecha look to Animated's exaggerated curves or Bayverse's robot birds.
I've always been meaning to take photos of my collection once it "stabilises"...but then there's always another cool figure on the way.
Thanks for the welcome, everyone!