What would the compression ratio be if I fitted 4wd pistons into a 2wd botton end.

I have just spent a fortune getting my bottom end lightened polished balanced cleanned. my 205 has had liners fitted and I have .25+ forged 4wd pistons to go in. A guy I spoke to said fitting 4wd pistons into a 2wd bottom end will lower the compression slightly??? is this true. I want to get the tops of my pistons machined down anyway so what compression ratio is the norm. I have a t35 stage 3 turbo if this helps with the awnser.