RE: cub ground roll
Wheel alignment can be a problem. Be sure to have a bit of toe-in on the gear. Exponential on the rudder also helps as it is easy to over control if you get to much rudder input. Cubs seem to have a liking for a slightly more nose heavy CG than many planes, try about with CG at about 25% chord until you get used to flying it. I strongly disagree with moving the the main gear forward as that will make landing very difficult with lots of bouncing with the resultant wing tip damage. You want the axle just ahead of the CG when the plane is in level attitude.