/\ well i disagree with the above, but it's your project.
you don't need to go lower compression, more power comes from higher compression, but puts more strain on the componants.
i don't really understand the last statement about the pistons should be the same, don't do calculations on erroneous information, get the componants and do proper tests.
and as for 'other' pistons, what pistons, where is the pin in relation to the piston and does is actually fit or does it need rod work to get it to fit, i.e. in the case of the XE pistons on zetec rods.
IMO 9.2:1 is a little high for a turbo and would not run more than say 7psi of boost, as i would imagine there would be loads of stress on the rods for sure, more compression means less margin for error on fueling and timing, which is why we all know we lower compression ratio.