I am in the same boat~ I have done the same kind of digging. The clumps are just to big for me to handle. I am wanting to get them out of that bed. So when the rain stops around here I am going to try a log chain wrapped around it hooked on my litte John Deere. I am hope that will pull it out. If not I will be using Round up! As far as the pieces go, I dont think it really matters, I have given this grass away before and only was able to cut off a small piece~

Cut chunks from the outside of the clump, in sizes you can handle. That's the best place to take divisions from anyway, because it's younger growth. When you've whittled it down with exterior divisions, the middle should be easier to get out. You can probably toss the mid-section into the compost heap.

At 62, I get a friend to help with the digging and use an axe to split clumps apart.

Just one more voice chiming in.
After digging around the grass we almost always split our large grasses before trying to get them out of the hole. Often just dividing the clump into 2 or 3 big chunks does the trick. Then, once out of the hole you can cut off the dead portions, if any and then divide into as many pieces as you require. My tool of choice is a splitting maul or a wedge - both used with a mallet. It is just easier for me & does the least damage to the clump. There is no perfect tool so, choose something that suits you.
There was a posting of Donn's that talked about a really good shovel for the job.

I have sooo many LARGE grasses that have to be dug & divided this year - I don't even want to think about it yet.....

Here is a link that might be useful: shovel

Thanks for the ideas (I will have to take notes on that link - great post). I was not expecting such a difficult job at dividing this grass!
I ended up getting some help. We did eventually manage to chop it in half before getting it out. It took lots of sweat, a little blood, and one broken shovel.

I thought you were supposed to divide every few years? Next time I will wait a bit longer.

seahorse

Hi everyone, Here's what I did. Took a shovel and dug all around the 2' wide grass. Soaked it down with the hoses a couple of times. I then took my husbands sawsall (unbeknowns to him) and with a long blade, I proceeded to cut about 8 pie wedges. The saw did most of the work. I potted up my wedges and gave most of them away. I'm about to do the same thing to another "large" clump of Miscanthus. They do get big. Happy Gardening, bayridgeri