Comparing mounting point on two different skis can be dicey. Are they the same length? Do they have the same running length? How turned up are the tips and tails? Etc. You can definitely ballpark it by aligning boot center mark (actual, current, or intended) and compare side by side. That was how I determined Atomic was bat shit crazy in their recommended mark for the Theory. I went further back than recommended but still not quite enough.
It is a shame more knowledge and discussion about mounting point isn't out there. I have experienced a 1cm difference making a huge different in my enjoyment of a given ski. I don't feel like I have enough knowledge myself, but I know enough that one mounting point does not fit all and I have experimented usually to much better results. And (such as my case) even a range of mounting points provided by the manufacturer may not match up as the ski manufacturer intended for all skiers, especially depending on style of skiing.
One big problem is micro adjusting is not possible, you can't remount .5cm back and redrill. You could get a binding that allows adjustments but those types of bindings are significantly heavier.
Good luck with your decision DackerDan. No one here can make that type of decision for you and of course you run the risk of making the performance issues worse if you go back too much. My opinion is life is too short to suffer poor performance so worst case you give it a shot, it doesn't work, and you decide to buy a different ski.