From a Cosworth spec sheet (doesn't list YB pistons) it looks like 0.003" to 0.005" is typical.
For high boost build I would use the higher clearance spec of 0.0045"

The Mitsubishi specs are with a cast Iron block - I would assume those specs would hold for a YB build as well.

Wristpin clearance of 0.0005" looks good (clearance spec in following data sheet)


http://tomitaka.com/Products/Engine/...ts%20v1.0a.pdf