VPN IPsec and MTU

HI,

we are Using VPN IPSec and we have some problem that the default MTU is 1392 and we have 2 Internetprovider witch not working with the default MTU, we must change it to 1390.

The Problem is that everytime when the Forticlient is started, the MTU is changed to 1392.

We change the MTU with CMD and "Netsh interface ipv4 set subinterface xxx mtu=1390 store=persistent"

The user dont' have admin right on the Notebooks.

it's possible to deactivate that Forticlient change the MTU on every Start?