Yes, use SATA cables with the 90 degree connectors and you will be fine.  You'll need a data cable and a power cable with the 90 degree connector.  I just installed an additional hard drive in the empty 3.5" slot and it works fine with the angled connectors.
I have added a 2nd 3.5 hard drive to the top cage but I cannot get the case to close with the power and SATA cables connected.  Have people gotten this to work with right angle cables?  It seems like even those would be too tall.  Or am I not doing something right? Picture of current cables I've used followed by some cables I will buy if I need to. [IMAGE]     [IMAGE]Will this fix it?   [IMAGE]
XPS 8940, 2nd 3.5 hard drive cage cables won't fit