Using a HeaterMeter on a cinder block Pig Pit

Hey guys, I've been a HM user for a while now with my Primo Grill. I'm cooking a whole pig this year, again, on a block pit I'm building in my backyard. I've been thinking about using my HM to control the cook by using my RotoDamper to force feed or reduce air flow to the pit. I was thinking of having a pipe run on each end of the pit which came out and joined in a T up to a fitting to connect to the rotor damper. I would drill a few holes in each pipe, similar to a grill burner, to feed air to the coals on each end.

This is the basic pit I built last year
http://amazingribs.com/recipes/porknography/building_a_hog_pit.html

And I was going to rig a way to get coals to sit on an expanded metal platform a little above the pipes, and have a way to both deliver the coals to each end, and rake ash out without opening the top of the pit.

Anyone ever used a HM to control a larger pit like this?

My guess is that type of construction will have enough leaks that the HM/RD will be irrelevant. If sealed up well I would think you would need something larger than the RD and a 6.7CFM blower. Maybe the RD25 would work, which has a much larger damper and can run blowers from 25-45CFM.
I've no experience with a pit like that, perhaps it will leak enough heat that choking down the air wont be needed? If the pit bleeds heat and you need to keep stoking the fire to hold temps you might have luck using an air burner type design under the fire with a larger blower and no damper at all.