I have had a win! So I cast a buckle in clear so I could see through it and find the problem points. From there I took scalpel to the mold and made from crude mods. I then cast a new buckle in a harder plastic which I also pigmented white. This plastic remains flexible for about 24 hours, so I have been able to open it up a bit as the master part is a bit too small to fit my ankle. I also took advantage of the softer form time to do the rough trims. After this sets up and reaches full hardness, I can trim it with the dremil.
As for the mold, so I don't have to trim each cast part, I will mod the master, cut out more silicone from the mold, re-insert the master and fill in the gaps with more silicone. As silicone only sticks to itself, it will bond to the existing mold. I will have use a release agent between the two halves.
I also modded the molds for the bubbles, so tomorrow can hopefully de-mold my first pair of bubble free parts.