If the point of the divider is to house two snakes that’s not going to work with the rhp as the sole heat source. I don’t think a 2 ft wide enclosure will give enough space for a proper gradient.
Pro-Products sells appropriately sized RHPs for a 2x2. They're 50w and are 12x10 (or so, I might be a bit off). I'm using one now for my boa and the gradient is perfect. 90 directly under and 77 at the edges of the cool side.