I work with chocolate and molds every day, right now I'm winding down my Easter bunny/egg production.
Here are a few ideas on molds in general:
-I loathe, hate, detest, want to do terrible things to the people who make/sell molds where you have to "glue" or melt the halves together again. It's a cheap cop-out, it's sloppy, and the joint is weak and prone to cracking or failing once packaged. Ironically enough, Callebaut sells these molds, and I have a pictorial on another website showing how I band-saw the mold in half, cut some bottoms into it, and drill some locating holes into it to make it into a practical, two piece, clip together mold. I've done this with about half a dozen molds now.
-Not much of a fan with the cheap thermo-formed molds, but they do work well for the first dozen or so times until the plastic cracks and fatigues. Bear in mind that you will always get a rougher seam with these, because the plastic is not capable of bending sharp 90 degree or even sharper angles--this is usually where the the side of the mold meets the lip of the mold, and the effect is doubled when both sides of the mold are clipped together.
-Even with the best rigid molds you will still get "flash" or minute feather edges of chocolate leaking out of the seam, regardless of how many clips you use. This is easily trimmed off with a sharp, cold knife.