In my opinion the GTR ballancing is unacceptable !
The higher weight of the FZR and the XRR increases the tyre wear and the tyre temperature too mutch.
My suggestion: keep all the GTRs at 1100kp and rule the ballancing with the engine power.
Example:
FXR = 490hp / 1100kp (default)
XRR = 480hp / 1100kp
FZR = 475hp / 1100kp
Its really no fun to drive a GTR with the ballancing as its now.