I've heard a lot of good things about the SOCOM stock from Ace, and it sounds like it would be a nice option for a variety of AR builds. However, I recently got the chance to fire my step dad's AR which IIRC was equipped with either a Magpul STR or ACS/ACS-L. I really like the sloped cheek piece, as I found it gave a solid, comfortable cheek weld. Then, one day I came across the MFT Stock Saddle, which can attach to a standard MIL/LEM style M4 stock and provides the sloped style cheek weld. Then this sparked the idea in my head that it might be possible to combine the stock saddle and SOCOM stock. The only issue that I can see is that there appears that there would be a lot of empty space that would likely need to be filled some how. Any ideas or suggestions would be greatly appreciated.

Here's a picture of the stock saddle:

And here's some links to the  products in question:
Ace SOCOM: http://www.brownells.com/rifle-parts/stock-parts/buttstocks/ace-m4-socom-stock-prod24960.aspx
MFT E-Volv Battle Stock Attachment: http://www.amazon.com/Mft-E-Volv-Battle-Stk-Attachment/dp/B009DPAZXK

I wouldn't recommend doing that. The Ace stock is adjustable length, and adding that as a riser would obstruct access to the adjustment button.

Personally I would just buy a B5 SOPMOD and be done.        
 

To me the stock is kind of back wards compared to a standard AR collapsible stock. The rear portion extends from a fixed tube which attaches to receiver, somewhat similar to a Magpul UBR. I'd end up securing the Saddle to the tube of the SOCOM stock rather than the adjustable back end. If all else fails, the saddle could be trimmed to fit the length of tube. I wouldn't have a problem with cutting up a $30-40 chunk of plastic to get it to work if that's what it takes.