Seriously, HA whirl comes with a friggin huge rail gun thingy and there's no way for him to use it? Unacceptable, but fixable. Here's an easy solution that won't force you to sacrifice anything you don't want to. One, Take this lego piece out of your collection. It is the one thing you'll need to sacrifice. I know the picture isn't the greatest, but it's one of those that attach via the brick based ratchet joints. The end is wide and has a small hole that goes through it. Basically, that hole is perfect for the pegs on Whirl's arms. Two, Cut off the ratchet joint connectors and glue it onto the side of the rail gun via superglue. Three, post onto your HA whirl. Any questions? No. Shoulder can still move freely and your HA whirl looks just that much more awesome.
Granted, I realize not everyone has it, but there are probably other lego pieces that would suffice. I honestly did this in about 10 minutes. It's not a big deal, but it's there for the idea.
I've seen another, more self-contained approach: attach one of his gatlings to his arms, then close the chopper blades around it.
Sadly that would mean that the chopper blades themselves would not be able to spin, which is something I wanted to maintain. Also the connection would be much looser.
