I may be missing something but I would be a little afraid of wood lagging a boiler with a flame burner under it on a horizontal where the flames can creep up.
No Frank, I don't think you are missing anything here that would make a difference. I agree that wood lagging on a flame fired boiler may not be a very good idea, unless the lagging is some insulative material that is non-flammable, or at least the bottom strips of the lagging are such that the flame can't get directly to the wood strips above it!
Did that make any sense?!?!