Ah the memories of the original Jack3d, such good workouts on dem amphetamines.
9mg/kg caffeine, jesus! That's 750mg! Even at the lower end of 3mg/kg that's still 243mg for me. I currently take 150mg.
Yeah most sports science things will cap it at 6mg/kg because the cost/benefit ratio is just not good for most people.
Usually you experiment at the bottom end of the range and see how adding a little at a time affects you, since some people experience adverse sides more than others or don’t build up as much of a tolerance to it. Dem genetics. IIRC the positive effects on output in the weight room for 3-6-9mg/kg scales somewhat with working in descending rep ranges, and the shift from strength to explosive power, so for an Oly lifter it might not be useful as they’d really have to push the advisable dosage for it to make any difference, where as a true bro might feel they get something out of the lower end of the recommendations and not need to go higher. I think you’ve said you’ve been doing more moderate to higher rep work, in which case more wouldn’t be better!