As an update.
I've found the best combination of bits for the PS to be the TbT delrin spring guide (which all arrived today), steel AA top hat and no power washer at all. Proper lubed up, smooth spring ends. At the minute output @10.8-9 ish, got that feeling it could creep up a tad, but not much. Overall, real good parts to the TbT kit, even though I've only used one, still 18 quid well spent. Power washers are so tight on the guide, they won't fit to the bottom. Guide itself couldn't be a better fit for the spring to be honest. Top hat was ok...but felt the steel one kept with the rifles