Geoff - here's my take on the issues you raise. It may be pretty well known to many out there, but I reckon it's never wrong to go back over the basics - somebody will be new to this instrument.
There are certain logical parameters, like - action not too heavy or too light (the guitar should not move across the stage when you operate a knee lever nor should you be able to operate one without feeling it). Within those, the "feel" should be what makes you comfortable while playing, otherwise you can build up mental blocks that hinder advancement as you avoid using this or that "difficult" change.
On an all-pull the different positions on the bell-cranks allow you to alter the feel. Pull-rods attached nearer to the cross-rod make the action lighter but travel is further; and vice versa. I like all the KLs to have (roughly) the same feel (and a short travel) but this can be tricky to achieve on multiple pulls. You have already noted that an additional "weight" kicks in when another string is picked up. That was often used (still is on older mechanisms) to provide a half stop on (for instance) the second string lower on E9th. By also hitching that KL to the 9th string (typically) and messing round with string gauges and where the rods fit on the bell-crank and changer fingers you can get that extra weight to kick in when the 2nd string has lowered exactly a half tone, where you feel the "stop". Then both strings can lower further until 2nd is a whole tone down and 9th lowered a half tone.
I don't know the tuning on your Carter, but could that trick be somebody's reason for the odd feel on 6 + 2? I have never been comfortable with that system and so I just don't use half stops.
The only other point I would make is about the lever position relative to your knee. Most guitars have some sort of adjustment for the angle of the lever off the cross rod. I like to set these pretty close to my knee, almost touching. Some prefer more space, especially on Unis where the left leg needs to cover a number of pedals. I have two additional left KLs near the centre of the guitar that operate only on C6th, and even these are close up despite having 5 pedals under control of the same leg.



