UPDATE: You need to do this with the current IRC FroYo build as well.
First things first, I have personally tested this with DamageControl 1.0, with Flipz's .03 radio, and found it increased my battery life by 30-40%. I am using the stock 1500mAh battery. Please note that the option to change the preferred network type is not available in 1.5 ROMs, as 1.5 is GSM only. (HTC hacked in CDMA support)
NOTE: when you first open the testing menu, it will show it as CDMA auto (prl). This is a visual glitch, in reality, it is set to GSM auto (prl). If your TWS is around 50%, it means it's GSM auto (prl)
First things first, go into Settings> About Phone> Battery> Battery Use> Cell Standby. Assuming your phone has been on, or off the charger for ~10 minutes, it should show Time Without Signal at around 50%.
Next thing, press HOME, and bring up the dialer. Dial *#*#4636#*#* (Do not press "Call"). After a second, it should bring up the "Testing" menu.
Go into Phone Information, press MENU, and tap "select radio band." You should experience a Force Close, don't panic, this was supposed to happen. Scrolling down shows that the preferred network type is GSM auto (prl).
What this means is that even though you are connected to a CDMA network, your phone is trying to find a GSM network, preventing the radio from sleeping, and causing excessive battery drain.
Remedy this by tapping GSM auto (prl), and changing it to CDMA auto (prl).
Now your done, your TWS should drop dramatically, and you should experience much better battery life!
Note: You need to do this every time you reboot.