[en] Highlights: • FLASH proton PBS has strong potential to be implemented for patient treatment. • Clinical proton PBS delivery parameters were extrapolated to high cyclotron current. • It is challenging to achieve >40Gy/s FLASH dose rate for field size >4x4 cm². • Scanning magnet slew and energy switching times appear to be the limiting factors. • Portion of the local dose can be delivered at FLASH dose rate. Proton Pencil Beam Scanning (PBS) is an attractive solution to realize the advantageous normal tissue sparing elucidated from FLASH high dose rates. The mechanics of PBS spot delivery will impose limitations on the effective field dose rate for PBS.