No, i'm afraid it's not possible to use Custom Edit with UV Surfaces. It can be done with XY Surfaces because Custom Edit stores the item's XY position, and then uses the surface to align on Z.
Instead with UV Surfaces, item's position is defined completely by the UV coordinates. When surfaces changes, item must be respositioned on space.
There are few possibilities in this case, except to play with UV coordinates until getting an acceptable result. With the default Surface settings (UV Transform->Align on, Direction = 0), items are scattered with X along U direction, Y -> V and Z perpendicular to the surface's normal.