KDE used to instruct HAL to perform the suspension/hibernation, so the script to modify would have been the HAL script SL used to perform the suspend. HAL does not exist in Gentoo/Sabayon Linux these days, though. Since KDE 4.5 or 4.6 (not sure which), KDE changed to using UPower and D-Bus. According to the Kernel developer's post
Re: [RFC][PATCH 0/2] PM / Sleep: Extended control of suspend/hibernate interfaces:
Richard Hughes wrote:NeilBrown <neilb <at> suse.de> writes:
> upowerd then runs /usr/sbin/pm-suspend.
> pm-suspend then runs all the script in /usr/lib/pm-utils/sleep.d/
> and the calls "do_suspend" which is defined in
> /usr/lib/pm-utils/pm-functions
So you could have a look at those scripts in that directory. But I wonder why suspend/hibernate does not work for you from KDE, as it's working fine for me.