Rarely used e on a career 707II .25 in Winter for indoor shooting , it had the rotating valve stem travel limiter style set up and shot 39g from 0fps to 999fps. I did know to start 6 clicks from highest for the longest string, then 2 added clicks after 6 shots ,..... Didn't use it that wat much though, 999fps avg for six hunting shots ( Chicken eatin vermin )was it's real job. Has a BUNCH of similar old Korean riflkes and just shot all pretty much on high.
I tried one .177 ( and don't recall the model) that That was a disc with transfer port holes in it type. It shot right at 6fpe, 11.8fpe and 19.9fpe I liked it so say Barn work at 6fpe and squirrel , rabbit , target work & field Target at "12" & "20" fpe.
Have an older AA410 .177 that has a "power tune" ( drilled for an Allen screw TP restrictor ) at PAG just to get it under 20fpe, it came shooting a full 23fpe , in .177! It has been set once and never toughed again. Used for field target and hunting and fun.
HATE the totally variable and non repeatable transfer port knob type! Worse than useless for me.
IF a rig has a factory power adjustment ( external ) it MUST be resettable to whatever given power so a chart can be made or better yet it repeats so close you'll just remember the holdover/clicks.
IF the adjuster just allows adjustment ( like well all used to do with DIY home care, springs, ports, ... ) and you've no idea where you are now shooting without a chrony workout, it would be a desired feature for me.
I like regulators and a set power level most.
John