Well I actually investigating about this matter, I found a interesting page talking about compatibility between those tremolos digs. Which mean what type of tremolos fits well on cavity of other and not.
On that page it shows pics of the successfull and unsuccesfull cases. The only problem it's that page is wrote on Italian. Here is the link World dot Wide dot Wet dot guitarmigi.it/_Tips/CompFloyd.html (I cannot post links now)
That page shows that Edge Pro and Original Floyd Rose Fits very well on the Edge III cavity and the distance of the tremolos studs is the same. The other ibanez (Lo-edge, edge) and Schaller don't fit on the edge iii cavity.
Another think is must of ibanes guitars have 400mm radius and floyd rose is made for radius of 10'' more or less. 10'' to mm is about 250mm so, you probably gonna be a problem of buzz or death notes with ORF on Ibanez guitars, excepts JS
, which use similar radius to floyd rose.
If you don't kwon what is the guitar radius, let me explain. The fingerboard is not flat, is curved from 6th to 1th strings in almost perfect circle. Image a line going from your finger board to the back of the neck and extending to the magnitude of the radius, that line is the radius naturaly. Then your fingerbord become a little section of the circle. If the radius changed, the fingerborad curvature change too.
That explain why you must probably have problems of excesive buzz or death notes with OFR. However, you can use Shim Set for Locking Saddles, it can be found in parts stores and are used to raise your floyd rose Saddles. If you use a OFR, you probably must buy a Shim Set.
The other think is the anchors of the OFR and perhaps Edge Pro are diferent to the anchors of Edge III. So you have to drill to expand the cavity of anchors. You can let the same studs of the Edge III, but I think a tremolo replacement have to reaplace everything to works fine.
I think that the Edge Pro is the best option, because it has the radius of most ibanez guitars and is more compatible, perhaps the anchors dimentions are the same.
For last, be carefull, there is a variation of Edge Pro which is or was used in JS
guitars which was made to works with diferent radius. Buy the standar, no the Edge Pro of JS