Auto mode for a vintage plane: not follow desidered path

Hi all
From few weeks i’m tryng to improving a vintage plane (majestic major) to fly with pixhawk. now it flies quite wall in all modes (stab , manual, fbwa rtl, circle…) but in auto mode in certain situations it is not satisfatory at all… in simple missions (like a square 200x200 mt it’s roll gives satisfaction but in survey missions the turn radius is alway bigger than what i nedd i also made test with the alternate line otion of MP but with no improvements… i changed RSLL P at bigger value (than the one proposed from Autotune) 0.9 >>1.3 i hade a wide roll angle 55° and a low number for L1nav period… what can i do more??
thanks for help

Please provide tlogs and/or dataflash logs to help troubleshoot your issue.

Here you can find a place where to download my last logs (sorry they are a bit heavy) … sp=sharing

Its hard for us to tune a plane without flying it and adjusting accordingly. You best bet is to slowly work your way through this
and make small adjustments until you get what you want.
Thanks, Grant.