As Deon evidently remembers, I posted a while back on the subject of using a triangular Sharpmaker ceramic hones in my Apex. I thought it worked out really well (and I was touching up the edge on a large Apogee with a highly wear resistant CPM-420V (S90V) blade, so this technique will work with any steel).
At the end of the Apex handle is a large ball. Just unscrew the ball and then remove the small cylindrical spacer between it and the adjacent hone securing clamp. Once the spacer is removed, the clamps will now open wide enough to accept the full length of the Sharpmaker triangular hone (point down, of course). And then just sharpen as normal.
I should add, however, that others have also reported simply using the stones supplied with the EdgePro on recurves with no problems. I prefer a slightly more polished edge, so the Sharpmaker stones work a little better for me in this regard.