If additive was any problem to the wear rate or a purpose made carpet it wouldn't be used as much as it is.
But does it matter if you are all on a level playing field? It does remove a cost element to someone on a smaller budget. Having said that you could argue that you could get away with running older tyres with the use of additive.
I guess you could go alone the lines of just using a tyre cleaner such as brake cleaner! That'll soften the rubber and the owner can't argue that will damaged the track if the tyres are going on it clean!!
