Sounds to me like you have some minor mast compatability issues here.
First, I would forget about the top of the sail.
The only way to get the batten above the boom cutout to be at the midpoint (fore and aft) of the mast at the same downhaul tension that gives you the scallop in the top of the sail running in to the tuning mark is to have a fully compatable mast.
You can control (with downhaul tension) the position of the front of the batten above the boom, but you cannot change the bend in the top of the mast which gives you the scallop.
I would worry much less about the top of the sail as there is nothing you can do besides try different masts until you get the correct tuning on the front of the batten above the boom at the same tension that creates the correct scallop in the top of the sail.
So, for the 8.0 m2, just downhaul it until you get the batten above the boom back to the mid point of the mast. This would be the max power light air "tune".
As the wind comes up and you want less power from the 8.0 m2 Retro, downhaul it some more until the mast is just able to pass behind the back of the mast.
More downhaul than this won't do much for you and may make the sail very "on/off".
For your 6.5 Retro, again there's not much you can do to get both of the tuning points
correct if your mast is too soft in the top.
So, again, since you can't change the bend characteristics of the top section of the mast, do the best you can to tune by the front of the batten above the boom and let the top do whatever it does.
You might want to check with some of the folks you sail with and see it you can borrow some different 460 and 490 masts to see if there's a difference in how your sails rig.
Wish we were closer together as I have several masts you could try and I'm pretty sure we could get your Retro's to tune correctly.
If you have any "back up" masts, you could try them as well.
Sounds like the bend characteristics in the top sections of your masts is off, the top of the 490 cm being a little too stiff and the top of your 460 being a little too soft.
Hope this helps,