Hey skumper. I can't be for sure but I'm pretty sure I saw someone ask the Same question about being able to use a short and wide pot and the answer was yes. I'd say go for it unless someone with more experience than myself chimes in. Can you get some close ups of both plants lady parts?
Edit to say that your current root ball is already so tall and you probably don't want to disturb it much.....?
Edit to say that your current root ball is already so tall and you probably don't want to disturb it much.....?