IMHO, no. You already have an elevated location for rope attachment.
IIRC, it's a deep V hull with around a 21 degree dead rise at the transom and usually and outboard motor. Weight in the middle will increase the wake size. You'll have to mess around with that.
Check out Alex Kinon's profile pic.He rode behind that ,and made it work,and had fun doing it.The boat is pretty much as you described.Fishing boat turned wakeboarding machine.
there are some kids i see out all the time on lake austin with a center console, might be bigger than 21' but they always have it piled high with friends and a pretty big wake. they always have big smiles on their faces, usually some young hotties in the boat too. it's not about the boat.