Go to the FSX forum on http://www.avsim.com.

They have all the tweaks listed. You can improve performance a lot but I am still not sure how add-on aircraft will work in FSX.

I am keeping an eye on new tweaks but still flying FS9 for all 3rd party add-ons.  ;)

Do not expect to switch to FSX until I get new hardware (a year or so from now ).

Having said that - for those of you that only do bush flying FSX DOES provide good performance (none or scant AI traffic and no resource-hungry airports.) Love the Beaver in the Horizon Simulation VFR demo.