If this is the floor plan below, where does the dehumidifier sit? I can see numerous options depending on location. You could poke a hose out through the exterior fridge vent. Rather than drill a hole in the floor, look for existing openings large enough for a hose like a gap around the drain pipe for the bath. sink. A city water inlet with a male-male adapter might work.
If it were me, I would def. never drill through the floor unless you have 100% verified there is nothing in the way. You *may* think it's clear but you don't want a surprise and end up with a big issue to deal with or costly damage. Maybe you could cut a 3-sided flap in the coroplast around it's perimeter somewhere. Then use some gorilla tape to close it up again.
Our KZ TT had some unnecessarily large gaps in the floor - large enough to throw a cat through... :R
I'd get a hydrometer so you can monitor the RH and not run the dehumid. more than needed.