Probably better is to scale hp curves rather than clip!
You might take interest in the suggestion I just posted:
https://www.gtplanet.net/forum/threads/power-limiter-by-flattening-torque-curve.306654/
Actually tuning a car way down with the power limiter will tend to make it very uncompetitive in the PP system. The PP system tends to use area under the HP curve for PP calculation so a car tends to gain an advantage in the PP system if it has an upward sloping torque curve. The power limiter gives a downward sloping torque curve for the area where the HP is flattened.