I am in 8b and I have two 9-10 footers in the garden...nursery man swore they wouldn't get over 6'
I knew better as there is a local one that is 30+'
As a bonsai I am not convinced you can make a long term tree out of them(they grow too much and don't back bud...couple days of shade and all the interior foliage dies). I gave up trying a few years back. If you were content to just let it keep getting bigger they might be ok for a decade or so but not worth the hassle for my garden.
I wonder if anyone can post a picture of one that has been in a pot for more than 10 years??
I do remember a nice one from northern Europe but it was rather large...4' maybe...and had just recently become bonsai.
If you have never kept one, which it sounds like, I think I would be hesitant to put any real money into one until I had at least worked with the species for several years...but that's just me
John