I don't see why the 5 is overkill "for dirt". The 4 had all the same features except the GPS is not standard for the 4. The laptop downloads are no different and the software for analysis is the same as all aim car and kart loggers. The 5 doesn't need a download key like the 4 but it's still the same stuff. If you need a logger with download to laptop I wouldn't even buy a 4 or the 5. I would go with the AEM AQ-1. Heaps more flexible and more capabilities and input channels for the same price. I like the aem software better too. Fwiw, the 5 is about 550-600 on eBay stores.