I have the XI3 9' 9wt and while it is not the same rod, I use 30ft of Rio T14 (420g) on it and it casts well, but to be honest it casts an Airflo 40+ 10wt saltwater line much much better! It also casts a Skagit head 450g Okay spey style, but it is not fun!
If you are happy with the 350g I'd stick with it, or only go a little heavier.
All the best.