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Yes, the focal point will remain the same distance from the primary mirror - so when you move mirror up the tube, the focal point will move further out of the focusser draw tube. So you don't wind in as far to reach focus. The only problem (apart from perhaps hitting the max out travel on the focusser for some eyepieces) is that the light cone is a bit broader at the secondary. Depending on secondary size, perhaps you lose a little of the converging light around its sides? Pulling the mirror down the tube just leads to possibly hitting max in travel before achieving focus.
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