When refering to the tanager ROMs it all depends which network/supplier as the SMART in the phillippines had the most recent but inless you wanted to use their network then you should never try to upgade to their ROMS.
The reason for this is that they SIM locked the phone to their network and prevented you from downgrading the bootloader so you could SIM unlock again.
Try orange ch (Swiss) as they used to have a good list of their ROMs whereas the Orange UK site has always been a pita to access.
As you actually have the dopod 515 this supposidly ran the 2003 OS and was the only Canary/Tanager to do so.
upgrading or in you case downgrading the ROm may not be advisable thing to try as you may brick the device.