how much shrinkage to expect

[luluzapcat]

I'm embarking on what's probably an over-ambitious project, involving making a custom mold, and making my own M&P soap base for the first time, and tinting it, and embedding the molded result in CP soap.

Anyway, in planning this I would like to know how much, if at all, I should expect the embed to shrink as it cools. If I'm aiming for a final embed of about .25" in diameter, should I scale up when I make the mold?

Thanks for any help with this!