Looking at the wheel base spec's on Team Associated site, the wheel base for a B4.1 is 273mm for a stock chassis. RC10B4.1 Factory Team: Team Associated - Champions By Design - Nitro and Electric RC Cars The wheel base for the Worlds Car edition that comes with a +8 mm chassis is 281mm RC10B4.1 Worlds Car: Team Associated - Champions By Design - Nitro and Electric RC Cars I just bought a used B4.1 to get into racing. I'm looking for a new body and chassis protector. When I measure the wheel base, I get 281mm which tells me the car has a +8mm chassis. My issue is the +8 chassis requires a longer battery hold down but mine measures stock length with no room to put the longer one in. I'm questioning what chassis this really is. Also, the buggy came with a JConcepts Punisher body which comes in both +8 and stock flavors so that's no help. Does anyone still have a B4 that can shine some light on this?