I thought About this reduced drag issue on the timetable spool last night.
Peter linked increased diameter being the key driver, but I think we missed something. Radius (or diameter) has a linear relationship to moment force, which is what we are talking about with drag capabilities. Therefore, with all other factors remaining constant, to go from a rating of 25kg to 15kg would require a 40% increase in diameter, which clearly won't happen on a reel without extensive modification.
So there is some other variable at play, and realistically that comes down to a weaker drag washer set or a different point of reference (position throught the usable depth of the spool) for measurement.
Anyway, I guess my choices are original part, SOM, and JM. how do these stack up against each other in overall terms?
BTW - do I recall reading somewhere once that shimano measure drag at the arbor? In which case this whole discussion about overall diameters is just a big red herring! Hahaha