Case fan layout/mods

[K808]

What would be a good size, and position for case fans? I have a full tower.

Im out of power connectors so only my exhaust fans are running, but i have the case side open and my tower fan blowing in. I went to compusa to get power splitters and they only had ones from belkin - 15 bucks!! I have an old comp so im gonna steal its connectors and make my own Y adapter.

i was thinking 120mm in the front bottom w/ intake duct. 80mm on the side. 80mm outtake on the bottom rear, 80mm on the top rear. Plus the PSU fan. I was thinking though, because the 120mm is sending in 100cfm, and the 80mm outtake (on the bottom) is only taking out 45cfm, wont that cause a build up of heat in the bottom of the case?

[UnseenMenace]

It is generally better to run a little positive pressure within a case as this keeps the air moving and reduces the chance of heat build up and hotspots. I generally prefer running 120mm fans as these can spin slower and still move as much air as most little screamers while remaining quiet.
As well as the connection situation you should consider the power requirements as well which is why I run two PSU.. ( 1 for the PC the other for the fans )

[The Overclocker]

bigger is better, always . get big fans and run them on 7volts cover the whole side of you case with them and as Unseen menace says, uses a second psu to power them, connect the green wire to a ground