Tandem,
The Mk 1 and 2 were 'essentially similar' in airframe, blades and engines, the main areas of a helicopter affected by ice. Therefore, read across would have been a reasonable risk to take by experienced Chinook aircrew in an emergency climb.
The Mk 2 is a D Model, it is not surprising that the FRCs were based on it. They were written by Boeing/Handling Sqn and included our FADEC drills.
I edited the post a number times without any hidden motive other than to add to my original thoughts. Not sure what element of history this would rewrite, as it is my recollection of events at the time. Sorry if it doesn't accord with yours. (The last bit was an edit)