Well, we've gone full circle on this one, and B737MRG managed to complete the loop quite nicely with the statement "a range of 1hr flying time at single engine cruising speed". Yes, there are many more complex ways of calculating a Climb / Cruise / Descent profile to be contained within 1 hour, but it must be remembered that it is to satisfy a legal requirement, not an operational one.
I cannot speak for all Regulatoty Authoritys, but the SPIRIT of the legislation is akin to the ETOPS requirement, i.e. the radius of action is based upon Cruise speed OEI, not the complete Climb / Cruise / Descent profile.
Regards,
Old Smokey