Its good, just a very intense version of a normal jelq.
Your working with more blood and pressure so go easy.
Also this IS mentioned in the constricter guide, wet jelqs clamped are there so this in essence has already been answered mate!!
ALSO when experimenting with CLAMPenis EnlargementD jelqing you have to keep it pretty tighly clamped(more than usual clamp sessions) because in essence you are not only engorging the clamped penis you are also pushing out blood (from the engorged penis) at a larger rate. If you stay stimulated it shouldn't be a problem but other wise give it an extra click.
WARNING: ALWAYS MONITOR YOU Penis EnlargementNIS WHEN CLAMPenis EnlargementD MORE THAN USUAL
your penis may go numb cold and black so WATCH IT!