DakMan
Taking note of your clarification, I would question the efficacy of shortening the tubes to terminate flush with the tubesheet. As it is, migrating Ice, when encountering the current design, has the ability to pass by the openings of the tubes and collect between them, for a time, held out of harm's way. The mod may have the advantage of collecting the tube openings closer to the Oil, (the Heat source), but the volume of Ice has nowhere to go but collect at the respective openings into the cannister. From a manufacturing standpoint, it appears a less complicated termination, (the Fix), simply with better access for the welder.
John Farley's anecdote about the Canberra is most instructive, a simple solution provided by a straightforward anticipation of the problem. A filter to remove solids (Ice) from the Fuel Flow, combined with a Heater to melt the Ice and return it? The Canberra was a very high flier; one should question the approach by Boeing/RR about the 777 design.
Over Run - I admit to the same experience. One who ignores any of his senses in flight is not using all his skills.
AF