Has anyone tried to fly one of these on a Merlin? Would it even be possible to balance it?

Jim,

Here's a recent thread on the topic from the 7d forum.

http://www.dvinfo.net/forum/canon-eos-7d-hd/468059-7d-merlin-steadicam.html

Thanks much Ken

I took a look - Maybe I'll just try mounting my 5D I on it to see what the rig feels like. Haven't quite decided if I'll get a Mk II or not, but if I can fly it, I might go for it.

it is very possible, even with the large lenses, but IMHO 5/7D is not the best camera for steadicam work.
when i occasionally fly 5D, i only use 35/50mm primes, they lighter and you don't need an extender, also you don't need to re-balance every time you change your working distance.
i only did this video cuz someone was asking how to balance 5D on Merlin with 24-70mm lens;

Canon 5Dmkii+24-70mm on Merlin on Vimeo

Results looked pretty damned good!

What I want to use it for are 20 to 30 second clips that will later be used for matchmoving

At present I'm using a JVC 110 on a vehicle mount to get nice smooth clips.