this might sound silly but i was trying to do 3 combo tricks before landing. What you need to do is a backflip and 2 grab tricks and that counts as your 3.
If you go to the second free ride map and find the orange marker and start the mission where you need to hit the targets you can do this on the first ramp. get max speed hold in the bumper and pull back to do a back flip then quickly do your 2 tricks and land it. Very easy here. Hit the ramp a little to the left so you have more time.