Firstly, Welcome Aboard.
The Insteon PLM template currently does not support X10. It tries, but I have never been successful. What I have done is this, until Insteon support gets better.
I have an Insteon PLM on a development box. I have 2 Insteon Lamp Dimmer Modules, and 1 Insteon Keypad Dimmer. Here is how I actually use them:
I have Hooked up to my core 1 cm11a X10 controller. Throughout the house I have several X10 lamp dimmers, dimmer switches, motion sensors, and XPS3 on/off switches. The insteon modules I have assigned X10 addresses for now. They are always reliable, and work much faster than traditional X10 devices. The Keypad dimmer switch I have has a local ON/OFF as well as 6 keypad buttons. These six buttons I have set to different X10 addresses, and it controls the X10 devices assigned to the buttons.
For example, The local switch controls the ceiling fan in that room, and the buttons:
1 - Kitchen sink light - A9
2 - Living room ceiling fan - A2
3 - Living room lamps - A3
4 - Foyer lamp - A4
5 - Master bedroom light (insteon lamp dimmer - linked the insteon way - also assigned X10 address B2 so the system can control it)
6 - Girls bedroom lamps (insteon lamp dimmer - linked the insteon way - also assigned address B3 so the system can control it)
SO you can use the high quality Insteon stuff for insteon devices as well as X10 devices.
This is currently the most reliable way to use Insteon and X10 with LMCE.
Hope that helps.