Optiplex 990 MT how to add 3rd hard disk

I have an Optiplex 990 MT,  I wanted to mount a third disk.  To mount the 2nd disk you need to get the carrier (DN8MY, H7283, GJ617, YJ221, and KJ516). The third hard disk is a little tougher since there is a nice mount under the 5.25 bays, but the screw holes are wrong, also the power cable is a little short.  I have a 5.25 adapter on order, but I slid a hd into the bottom 5.25, secured it with 2 case type screws to hold it. works, temp went up a little to 110F.  Power cable then works also.