The are four L-brackets that go between your base and your sides (8 screws into the MDF). Are you also screwed into your base from the outside of your MDF? If you only have the L-Brackets right now, you're not going to support the weight of the cab. You look like you've done a good job, so I imagine you have more screws into the base from somewhere, but I thought I would ask anyway. Good luck.