I have a Multitech and Starcom Advance.
When I bought the lid at the Excel I went straight to the Starcom stand to buy a headset and to ask them to fit it for me.
Their advice was NOT to use a boom mic as these are designed for open face lids. The boom is quite thick and you will probably need to "carve" a groove in the underside of the cheekpad in order to make it fit without the pad popping off. You would also need to adjust the boom every time you put the lid on. I was with Wapping of this parish (an Autocom and Multitech owner) and he agreed that the boom mic can be a bit of a pain.
Invest £20 in a "bud" type headset and stick the mic on the chinbar.
The wiring can easily be pushed into the gap between the shell and the lining using a lolly stick or something similar.
I have used mine a lot since January and it works perfectly. In true "boy" fashion I have the full kit - ipod, SatNav, walkie talkie (hardwired into the battery under the seat) and bluetooth mobile phone, all of which work perfectly. The PTT and volume control were good "investments" as well! I must be their best customer ...