Go to the LS races and start "Little Loop", and you will be spawned on an NRG which wheelies and stoppies much better, you will be able to do RADsテつエ for eternity... I've done one that went a whole lap around the LV highwayテつエs outmost road and onto the hill where everyone breaks the WRテつエs for height. If you fall off or leave the bike, it will start acting as the normal NRG, so just blow it up and start the race again, then teleport to the stunt spot.