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Well, here is my thinking. The focal length of the primary mirror does not change. The distance from the surface of the primary to where the image forms is unchanged, regardless of where the converging rays bounce off the 45 deg diagonal secondary mirror. However, the distance from the central axis out to the image formation point will change, depending on how far from the primary the rays deflect 90 degs off the secondary. The effect is that the image is formed higher or lower in the focusser. Thinking again about what you said - if you had to move the secondary an inch up the tube, the focal point should have moved an inch towards the tube axis, ie. deeper in the focusser. Hence I don't understand why you find that the eyepieces need to be higher in the focusser. Just check again without the barlow. You can always loosen the clamp screw and lift an eyepiece up (and even out!) to see where the image comes into focus.
By the way, does the new focusser look "square" to the tube - 90 deg? Obviously if the focusser is pointing up or down the tube. the secondary will appear to not be directly beneath the focusser.
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