How do I improve the battery life of my Inspiron 14z under Ubuntu 12.04?

This laptop gets 4-5 hours of battery life using Windows (e.g. here). I've removed Windows, installed Ubuntu 12.04 and the initial battery life was only 2 hours. With some tweaks (described below) it's still only ~2.5 hours.

For reference, the laptop is the latest model of the 14z:

• i5-3337U processor
• 32GB MSATA, 500GB HDD (5400rpm)
• AMD Radeon HD7570M graphics card

I have put ext4 partitions on both the SSD and the HDD, and have mounted / to the SSD and /home to the HDD. I also put a 24gb linux swap partition at the start of the HDD, though I figure this won't be used all that much (the laptop has 8gb of RAM).

After googling around and reading Ask Ubuntu and other sites extensively, I have done the following steps, and they have improved the battery life ~30 minutes (exact improvement not clear, but battery life is still nowhere near 4-5 hours).

1. Installed Jupiter (and set Performance to "Power Saving")
2. Installed laptop-mode-tools
   • cat /proc/sys/vm/laptop_mode now outputs 5 (previously it output 0)
   • But it's not clear that this will help: AskUbuntu question
3. Turned down the brightness of my screen from full to 1/3

Other things I have heard about but have not tried for fear of frying the laptop or my linux install:

• Add "pcie_aspm=force" at the end of the line with "quiet splash" in /boot/grub/grub.cfg
• Enable ALPM, but it may already be enabled in 12.04?
• Enable i915 framebuffer compression
• Use a propietary driver for the graphics card? Turn off the graphics card? (what would happen if I relied on the internal Intel bridge?)
• Use TLP?
• Spin down the HDD more aggressively (howto, but I think laptop-mode-tools does this already)

The only other thing I've noticed is that plastic just above the F5, F6 and F7 keys gets really hot. According to Jupiter my CPU temperature is only 69 celsius and the System Monitor shows CPU load at 7% so I don't think it's the CPU. Maybe it's the graphics card?

Also, I've set up MongoDB and LAMP on the machine as well. When I run powertop MongoDB is high in the list, but I'm not sure if that's relevant to battery life because I'm not actually doing anything with MongoDB most of the time.

Edit - Additional info as requested

$ lspci -nnk | grep -iEA3 "(graphics|vga)"
00:02.0 VGA compatible controller [0300]: Intel Corporation Ivy Bridge Graphics Controller [8086:0166] (rev 09)
    Subsystem: Dell Device [1028:057f]
    Kernel driver in use: i915
    Kernel modules: i915
--
02:00.0 VGA compatible controller [0300]: Advanced Micro Devices [AMD] nee ATI Thames [Radeon 7500M/7600M Series] [1002:6841]
    Subsystem: Dell Device [1028:057f]
    Kernel driver in use: radeon
    Kernel modules: radeon