Thanks for the recommendation
Didn't you say you were using the 250GB drive that came with the server? In which case the recommended brackets are no good for you as they're for 2.5" drives (laptop, SSD etc) whereas you're using a 3.5"
5.25 to 3.5 adapters can be bought for as little as 2 quid. No matter how much of a cheapskate you are surely you can afford that Got to be better than the disk flapping around inside the case. SSD's don't need to be that firmly mounted, but mechanical drives do really.