An 'insert' cable should work just fine for this particular application.

The TRS side of the insert cable goes into the keyboard stereo output.

Then the two TS sides of the insert cable go into the unbalanced 1/4inch inputs on the fostex onchannel 2 and 3. In otherwords, you'll be using two channels up for this keyboard... which is what you have to do when your mixer doesnt have a 'stereo channel input' as many mixers don't.

Then you have to pan channel 2 full left, and pan channel 3 full right.

You don't need to use the XLRs, in fact, it's a bad idea to do so. Get a standard insert cable - this has a 1/4 inch TRS jack on one end and splits to two mono 1/4 inch jacks on the other. Plug the TRS end into the keyboard stereo headphone out and the other ends into two of the unbalanced 1/4 inch inputs on the Fostex. The tip is the left channel and the ring is the right. Pan the two channels hard left and right, as appropriate. If the cable isn't long enough, use a stereo 1/4 inch jack plug to jack socket extension.

That said, the MR8HD is not the greatest bit of kit on the planet.

Edit: Mises' post snuck in as I was submitting this one.

A big thanks to both of you and this makes perfect sense. Also, I do realize the MR8HD is not the greatest, but I wanted something affordable, portable, stand alone, and simple. It will work for me for now... I'm using it simply to track and then dumping the .wavs onto the PC for editing and mixing.

Thanks again for the explanation. I really appreciate it.