Hands Off test VS bar drop?
 

I know Steve Hogg mentioned reach and bar drop can affect the hands off test. Just did some experimenting, results seemed pretty extreme: With the bar 5 cm below saddle, I can pass the test with tip-of-saddle 7.5 cm behind BB; at 6 cm drop, I had to get it back to 9.5 cm; with a 7 cm drop, an 11.5 cm setback. Does that seem right? Or, could it mean something is wrong with my fit, causing that to happen? Did a couple uphill repeats to check speed/power. The 5 cm drop/ 7.5 cm setback was nearly 4 mph faster up a 12% grade VS the 7 drop/11.5 setback. Am I safe in assuming that means the former is a better fit than the later? (And since I live over 600 ft up the side of a mountain, I'm MUCH more interested in speed/power/efficiency than trying to get low and aero!)

When I increase or decrease my drop, my pelvis rotates forward or backward a bit. This results in my comfortable sit bone support point to move forward (greater bar drop) or backward (bar higher, closer to saddle height). That necessitates me to move the saddle backwards or forwards (respectively) to get my center of gravity back where I want it (i.e. to get good Hands Off results). From my point of view, what you did is pretty natural.

I can't really comment on the size of the changes you had to make. Were they all fine-tuned positions? If so, I think that's just what your body wants. It's the boss.

What is this Hands Off Test?
For climbing any significant hill/mt a power position is favored over aero. However, speed - listed as a priority - when not climbing, necessitates reducing frontal area, so: getting low, flat-ish back, rounding shoulders, lower head, bringing hands in toward the stem, knees in, etc are important. How aero you can get without sacrificing power is one major benefit to training with a power meter.

All your listed drop/setback numbers are confusing (to me) and not likely to create a 4mph difference, unless one of those positions creates discomfort. If you can tolerate a 4cm difference in saddle setback with no change in comfort (over an entire ride) you are lucky to have such flexibility. Climbing better is a function of power/weight and pedaling efficiency. We all work on the engine for better power, fewer work on spinning smooth circles under the duress of a steep grade. Also, not sure how you accurately compared power output with a couple of hill repeats; my power drops with repeated hard efforts. The bottom line for most non-racing 'athletes' is to find a position of comfort first and make small changes from there to accommodate a faster ride given the terrain on your course.

Not sure if my rambling helps. You know most of this already. Not sure anyone can answer "former is a better fit than the later?" from your limited data, especially without pics or a video.

edit: additional thoughts - many saddles aimed at the 'performance rider' are longer than a touring saddle to accommodate the fore/aft shift needed in different riding situations; maybe enough to cover that 4cm range you tested without changing the setback. As to the handlebar height - I like being in the drops for a reasonable percentage of the ride so I position my bar height based on riding comfort in the drops, not riding on the tops.

I don't have a link to share for Steve Hoggs' blog, but here's the gist of it.

One of his views of good position is that the rider should not expend energy holding up the torso, body balance should be used to minimize those forces. So like a skier in a tuck, you locate the butt rearward from the feet (BB axis) to ultimately get the cyclist center of gravity ideally over the BB when in a low position. For me with a lot of excess upper body weight that means a lot of saddle setback or a very shallow seat tube angle.

The test for this balance condition according to Steve is to ride normally in your low position (or your preferred position) and lift both hands off the bars when it's safe to do so. If your effort to hold your torso in that position is very low, that's very good.

At the same time, if at that moment you tend to slide forward on the saddle, you probably need a tilt up.

After that you adjust the stem/bar position for arm comfort, handling, and whatever else.

It's not my idea but I like the results. Maybe I just have a weak core, but this works for me. Forward saddle positions do not.

I agree with most of what you're saying, I'm just responding to you asking "wtf is it?" I hope this helps.

For 1 cm changes in handlebar height, your changes in setback seem rather steep. On the other hand, you're starting from a fairly high position and just scratching the surface at getting somewhat low. Also, your starting point, 7.5 cm behind the BB, is rather forward unless you're quite short or your saddle is unusually long in the nose. What is your pedaling technique like--are you pedaling circles or primarily pushing down?

Any change in position requires acclimatization for both supporting the core and turning the cranks. Climbing steep grades will probably be the activity most resistant to changes in position because it's intense, it involves the entire body, and the entire body has been trained to do it the way you've been doing it. Doing it in a different position takes some re-learning. Better to test changes in technique over flatter terrain, and gradually.

My advice is, handlebar drop is not as important as back angle and reach to the handlebar. Aim for a 40-50 degree back angle, because that's where the power is, and a 90 degree angle from the back to the upper arm, because that's where you can pull on the bar for more power. And if you're not there yet, go in steps, and give your body time to learn the new technique before you test it.