Yeah, the only feeling in the F-4 are bobweights on the pitch axis. The F-4 has a artificial feel system for pitch.
The roll axis has a Constant Spring load. There is no real feedback from the control surfaces.
In terms of the F-4, the overall forces are made a bit weak for use with the rhino.
Best way to solve the slippery feeling is to go to DCS special option and have a look in the F-4 options.
You can turn up FFB up to 500% for roll/pitch.
Mine are set so Roll 280% and pitch 190%.
This all with 95% spring set in VPconfig