Live support says its fine...
Patrick: Hello David M,
Thank you for waiting and welcome to Cooler Master Live Help!
Your live chat session will be available in the Support Ticket section of the CM Fanzone at the end of this chat.
Please hold for one minute while I review your question.
Thank you for your patience.
You: Thank you Patrick
Patrick: Hello David, Yes this is perfectly normal due to the design of the mounting hardware
You: So it should move around and hang a bit.
You: It doesn't seem very stable.
Patrick: Its normal, its because the EVO has a pin in the center of the heatsink so it will move slightly
Patrick: Its very stable, no reason to worry
You: Okay. Thank you for your time.