65mm will be ok for road & dirt use..

For off road you are sprung to hard...
300 of travel you should have 100mm rider sag..
rider sag 33% or 1/3 of travel.. static sag 35mm bike under it's own weight,no rider...
The bike has to have travel in both directions not sit at the top of it's travel..
back the compression damping off it may help
New springs will most lightly be required if
you want a more offroad set up...

i have Showa USD forks in my XTR..
had them revalved as the MX set up gets
to hard to quickly for large jumps etc..
MX tracks are quite smooth.. no ruts/rocks/tree roots
that require a supple , controled travel thats more linar
in the compression springing / damping though out the travel...

__________________
Harley Davidson..
The easyest way to turn gasoline into noise with out the side efect of horse power...