I have no comment to make about the rack itself, but if you can't do fine adjustments with the safeties, you could do it with the deck underneath you: Sections of horse mat cut to the right sizes can give you a (small) number of 3/4" increments to play with underneath the bench (with similar adjustments for your feet). There are also 1/2" mats of the same material out there, if you want, though I wouldn't expect the difference of 1/4" to matter between the two types.
It's the same for any exercise, really, if you do it right, e.g. for the hooks... Just don't have yourself walking out a weight while making an unstable traverse, and make sure the surface is stable enough.