Screensaver and power controls

[Mark]

I think this is the last glitch I'm currently facing with U10.10 - so
far everything else is working beautifully - it even reinterpreted my
personalized metacity theme from CentOS into something I could modify
enough to work well and it has no trouble at all recognizing my HP
J3600 as a scanner AND a printer, but I digress....

In the screensaver, there is a slider for how long to wait before
considering the computer idle and locking the screen.  I like leaving
this long because under CentOS, mplayer and the browser plugins that
play movies don't disable the screensaver (xine did), so I have that
set for 2 hours.

However, in the power options, I can't set the screen to stay on for 2
hours unless I tell it never to go off, which I'd rather not do.  In
CentOS, I had the screen power-down set for roughly half an hour after
the screensaver kicked in. Off hand, I can't remember if this was an
explicit 2:30 setting or if it was just 30 minutes (after lockup).
Under U10.10, I can only set it for 5, 15, 30 or 60 minutes, or never.
 I don't get the sliders, either, just a field with fixed values from
which to choose.

I'm sure there's a way to tweak this if I knew where to look and what
to look for, so can anyone point me at the right config file, or is it
really limited to the listed values only?

I tried the Power Manager in System->Preferences, but that doesn't
address this issue, and I'm not at all sure where else to look.

Thanks.

Mark