i found that gr9's were too thin and have too little pedal to shoe friction for my liking when i used powergrips.

with powergrips, you slide your foot in diagonally and twist straight to get them tight... but i found with the gr9's, when i went to skid or skip, it tried to pull my foot back to the diagonal angle. maybe it was just me.

also be very careful with the little metal extension piece. many people have broken them immediately trying to get them tight.