For me ship lap in all its wonders is aship that has alreadty sailed . I think real ship lap was never mant to be inside and all the rest is just planks put on a wall and in this case spacds a bit apart so Iguess if you must I would use an MDF plank that is finished on all sides and then paint the wall . I guess maybe I need to know what the finished look is that you want .

Windsor one is a great product- all the trim in my house and my office is made from it. Why not mdf though? Likely cheaper? As Patricia points out there are other ways to create an accent wall.