This is a work in progress remix of: http://www.thingiverse.com/thing:241977.
The new plates are meant to use these arms:
http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR1.TRC0.A0.H0.TRS0&_nkw=+HMFS550&ghostText=&_sacat=0

The plates were streched by 20mm in both the front/back and left/right directions and the arms are marginally longer than the stock DJI arms (Dissapointing).

There are two versions of the bottom plate. One has tall risers meant to keep the stock spacing in between the plates, the second one was shortened a bit for asthetics. 9" props are pictured without motors , 8" props to be swapped out

There are other arms that are much longer and are a direct replacement for the original design that would allow even bigger props if needed. http://www.rctimer.com/product-845.html My modeling skills are limited, but it flys :-) Still working on the tall bottom plate to clean it up a bit. Dan