Japanese Red Dragon in a container

[Southpaw]

I have a Japanese Red Dragon currently in a 13x13 in garden pot. I'd like to take it out of this pot and put it in one more ornamental, but I'm not sure if I should increase the size of the new pot, or leave it in one similar size? I don't know how large the root ball is as I have not taken it out of the current pot which it was purchased in about a year ago. If I change pots, should I got for one that's the same in HxW (similar to the current shape) or one that is wider and more shallow ( like a big bowl).
Thank you for advice.

 

[oneeye]

If you add more soil than you are using now you will raise the water volume. If you use more water you will need to reduce the watering frequency to make up for the extra water. Again you can add more soil just let it dry more before watering. Don't plant the plant too deep in the new pot keep it up where the root flair can be seen.