Took me five attempts at getting logged on this site..think I am unwelcome.
Why not just stick to the Lycoming handbook. If you have to preheat take the machine where you can use a popane fired 230/110V space heater on the front end and do it that way.
Of course I realise a lot of people who own these machines are not artisans. It is going to cost you money what ever you do.