Originally Posted by Karl

Depending upon fuel type used, I would recommend somewhere in the 11.5:1 for fast road use, and this will be fine on normal cast pistons. The easiest way to achieve this is by skimming the head by an appropriate amount. I can't give you any figures as you will need to burette the head chamber volume and work out your current C.R.

Regarding bore size, 93mm is the safe maximum, though I have built many 205 blocked engines on 94mm bore with no issues. If you suspect bore porosity then it is best to liner the block anyway, and then you can run up to 94mm with no issues.

Hope that helps.