Update: Got the RB Continental. My Guild X-500 fits in there but it's still a tight fit... this guitar is HUGE!

But the guitar does fit and the bag is great - very sturdy, you can kick the bag and nothing happens to the guitar. It's also fairly light, perfect to carry valuable guitars like my Guild to classes, reharsals, gigs... It's a little tall on the back but nothing relevant for me.
My hardcase and regular gig bag are useless now... I will buy also a Mono for my 335, I can report then.