Modifications of this type can be technically challenging and will almost certainly void any manufacturer warranty and have the potential to damage the modified device permanently.
However, disassembling the case is complicated by 5 small metal tabs, not mentioned by most online instruction pages: two on each side, and one on the back just above the docking connector, which must be released as one of the first disassembly steps (for example, by inserting a very thin shim and pushing it gently down, while pulling the bottom panel down enough to clear it).
Many companies that supply PDA parts also provide their own guides for battery replacement; these are usually less radical and require little or no actual modification.
PalmOne released a Power2Go modification which allows the palm device to receive charge from an external battery pack.
Homemade devices with higher mAh power supplies have been made by some enthusiasts to increase the external charge.
However users who uses Bluetooth and Wi-Fi extensively will find that even with underclocking, battery life is still rather short as wireless usage tends to use more power.