Cabbage Palm Pot size Plant size???

Hi, I've got a cabbage palm (i think it's a cabbage palm) We've had it nearly 2 years now, it became root bound in it's first pot (about the size of the pot in this generic picture)

So we potted it on into a larger pot, i'll get a photo later, ours never got to the size shown in the photo in the smaller pot before looking pretty drained and unhealthy with a massive tap root exiting through the drainage hole.
Now it's in a bigger pot, i'm wondering how big should i expect it to get before becoming root bound again, it seems to have stopped growing again.
Obviously i'll get a photo of our specific one, but what pot size should i be using for say our plants probably 3rd year, we'd like it large, it's nearly 6foot including pot now, but the pot is say 2foot high.

 

you can keep in a small pot if you feed them every week and keep well watered throughout the summer

 

I think if you really want to pot grow you would be best using one of the coloured leaf varieties, they tend to be smaller and more tender, but better for pots.

The usual green, species, type just needs lots of root space to do well, so best planted out in the garden.

Whichever you choose, pot growing will only be OK for a few years.

 

What an incredibly moody looking picture!


Thats my lonely cabbage palm out front, the lower leaves are starting to yellow and it's looking sad (like last time it was rootbound) but that pot is fairly large!
Under the pot is a stump from the last owners tree that once grew in the same position, the pot is balanced on top of that and some gravel. So just planting it there is out of the question.
In that pot it's about 6' high