just my opinion, but to me the whole point of spawning redheads is to allow the parents raise the brood. and for me to watch them do it all. watch the fry learn to enter and exit parents mouths. and watch fry learn to swim together like a little herd and follow parental signals about safety zones etc. I wouldn't even spawn them if I have to remove fry and miss the Show!
your tank is smaller than mine, but so is your group. I would remove Pleco. make a sort of visual "barrier" (like a fence of fake plants) which the pair can guard fry inside of it. Do that around the location parents are already using, allowing generous room for the pair to work inside. let fry learn to forage and run to safety of parents' mouths until they are too big. Parents will fight off other redheads for their space. When I did it, my geo group of 7 was in a 75G with 2 heckelli and no bottom feeders. Parents, after a period of learning tries, eventually forced all other fish to the opposite side of tank.
IMO, it is frustrating the parental learning curve to let them succeed to the point of a good beginning and then cut them off by taking their fry. Like I say, just my own view.... and, specifically, on redhead/ mouth brooders. There is SO MUCH social interaction to their natural method.
IF you feel totally compelled to remove fry and raise yourself, I would still leave at least half in the parents' care. BUT stealing some may scare the parents enough that they will eat the ones you leave. young pairs do that when invaded. It's your toss of the dice.