Adjusting a manual toplink is such a pain in the neck, that for me, it basically never got done. Just pick a middle of the road setting and go with it.
My vote is for an hydraulic toplink. The easy, extra control when boxblading or brush hogging is truly amazing. The hyd. toplink gets used twice as much as the 3PH lift arms for "on the fly" brush hogging adjustments. Neither the brush hog nor the boxblade are as exciting to use a backhoe or even a front loader, but an hyd. toplink transforms their functionality from static to dynamic in a way that's easy to appreciate and enjoy.
OkieG