Thanks everyone. At the moment cost is the issue, I wasn't clear that it see this as an interim solution. Will be getting a Perdix and use my two SPG routed down (not lollypopped) the tank once I can spare the cash. Have tried selling the PPX but there isn't much interest at a price that I would need.
if you don’t need the air integration, you can look for a used Petrel. Bigger than the Perdix, but you might be able to find one for $400 or so.