Hey - I realize I'm necro'ing a very old thread, but I actually have this EXACT issue; but with the solution apparently not working out.
See, I think I ended up getting the very mounting bracket that is linked there. But when I remove my internal drive bay (also an Antec 900), I can think of no way to screw it in such that everything fits, save maybe using a power drill to resize some of the screw holes. To help along, here's an image I took of the drive bay sitting outside the computer, with the bracket (SSD inside) sitting on top of it.
My logic here is that you can see the large screwholes in the bay, which take big, long screws to go inside. (I actually got a number of these spare at one point). Those four big screws in the mounting bracket are used to hold drives (the bottom one takes longer screws, the top are shorter) leaving only those smaller screwholes left, which don't fit the aforementioned long bay screws.
I feel like I'm missing something here, or maybe it turns out I have a different bracket. I was going to get another on Newegg for Cyber Monday, but I want to be sure I'm getting one that will fit properly. (In the meantime, the SSD sits inside my system with nothing securing it, which I feel a bit precarious about. At least they're sturdier to a degree)