I have asked around for you, Tom, but I don't think anyone here knows the answer. If you are worried about the leeway of the coin in the capsule, you could try filling the space with sewing thread, using a pin or a needle to push it in the space between the coin and the capsule. Be careful to use artificial fibre only, since natural fibre may contain fats that may affect proof coins. Be careful also not to scratch the coin with the pin.
Peter