Not sure about the GRP's but over many years we never found anything better than schumi yellow minipins ! Infact I think
the yellow minipin tyre was conceived at the worksop meetings.. Any oldy schumacher people may or may not confirm!
We Ran anything when it was a cow shed across the road " now the car park!"
Then when we moved into main building think we started on cut blues then blue minispikes then yellow minispikes. Then the yellow minipins !!