The woody part of the core will dull the heck out of your knife and your food processor blade, it will be very difficult to cut, wont powder, the wood and the pith inside it contain very little alkaloid but will add to the plant mass that makes extraction less efficient. Thats why nearly everyone removes the core. Including the core in the extraction is just difficult with no reward.
After cutting off the spines, what I do is cut it in half the long way through the core and through high points of opposing ribs [this is an important detail that speeds drying], then cut wedges the long way through the high point on each rib. Once the stem has been reduced to long strips of adjacent half-ribs I peel out the core and throw it away, then take a bundle of strips and cut them into 3-5 mm thick slices. Thinner equals faster drying. Dont have the waxy skin layer against the cutting board or facing the ceiling as that makes them hard to cut, have the strips on their sides when cutting. 3-5 mm Thick slices will get fully dry in my food dehydrator in 8 hours when its set to 68° C as long as I dont overload the dehydrator.
Mescaline is very stable, crank the food dehydrator to its highest setting or near to it.
If reducing to a powder scrutinize the chips to make sure all of them are really dry.