Hi Ry,
Nice mount. You did well for the first time.
If this phal is a larger sized one and not a mini I would mount your mount on a larger piece of wood or cork. I do have some of my phals mounted on both and I tried to size the wood mount according to the mature size of my phals. I would use wire to attach them together. After the roots grow around it you won't even be able to seee the wire. I use brass 16 gauge wire since it will not rust. I also use it to attach my chids to the mounts. Bonsai growers have it. Let me if you need a lot and I can tell you where to find it. I buy it by the 1# spool.
Using twine works as long as it does not rot before the roots take hold. I only use fishline or the wire. Using fishline is good since you can cut it away after the roots are established and its kind of invisible being clear. Usually I wait about 8 months or longer. Depends on the plant. The wire stays permanently.