hey guys!! need your help, i'm trying to open the ibanez tsa 15h head to try out different tubes, but i somehow can't get it to open... maybe the tolex is just too snug? anyway, i've removed all the screws but still can't open it. I just want to confirm if i need to open up the back side of it. Anyone have any success with this and maybe other similar heads? thanks for your help!! p.s. i can see the tubes on the back, through the vent..