yes, the crown on a gen exp II is smaller than the crown on a sub. as far as the width. it's narrower. That's supposed to be like that. Yes, you can absolutely put a gen crown on there. I would also put a gen tube too. I believe if you got the 2836 Asian or swiss or 3187 you should be able to. but not absolutely certain that the tube OD is the same but I am pretty sure it is. but might have to check just to make sure. but as far as I've heard all case parts should be interchangeable with the gen. That's for the Noob best edition not for the cheapies like the 21j or 23j versions.