Originally Posted by suzukipro

Very likely on indoor at least, it just works better for me. To add insult to upgrade injury I just assembled the new C, D hinge pin holders and the rear gearbox won't drop in the recessed chassis area without the C plate hitting the back of the battery tray. The .4 Chassis must also be slightly longer or have things offset compared to the .3 Chassis. My $300.00 upgrade just turned into a $400.00 upgrade due to the need for a new Chassis.

Do Not Upgrade your .3 to a .4, unless of course the kits are out of stock and the parts are readily available...