Gents,
While I am always up for a conspiracy theory and the discovery of little elves that spread "anti-grip" between meetings, can we take a look at this objectively.
A model car club carpet does not deteriorate at the rate the level of traction dropped over the course of one week. And I very much doubt that additive on tyres is causing "carpet whisps/fibres" to remain on the carpet, reducing grip.
My feeling is that the level of traction we find on a week to week basis is more to do with how much muck and dust gets trodden into the carpet between meetings. (Archery runs Tuesday and Thursday...Anybody seeing a pattern here?) Rather than people running additive. This might also explain why we see a sharp drop in grip levels over the winter when the archery club moves 100% indoor when previously we have thought it may be something to do with the ambient temperature.
As for foams vs. mini pins and cut staggers. I'm going to run foams as I get a bit hacked off with fresh rubber of some form week in, week out. I'll let you know if i go quicker on them.