If you leave the skin on I wouldn't bother adding cure to it, it woould absorb muck if any at all. Also you want to reduce the amount of cure by 10%.
Here's a quote from the USDA's Inspectors Calculations Handbook
< Pumped, Massaged, Immersion Cured, or Dry Cured Bacon (rind-on): The
maximum limit for ingoing nitrite and sodium ascorbate or sodium erythorbate must be adjusted if
bacon is prepared from pork bellies with attached skin (rind-on). A pork belly's weight is
comprised of approximately 10 percent skin. Since the skin retains practically no cure solution or
cure agent, the maximum ingoing nitrite and sodium ascorbate or erythorbate limits must be
reduced by 10 percent. For example, the maximum ingoing limit for nitrite and sodium ascorbate
or erythorbate for pumped pork bellies with attached skin would be 108 ppm [120 ppm ! 12 ppm
(120 × .10)] and 495 ppm [550 ppm ! 55 ppm (550 × .10)], respectively.