Some good hop ups are heavy duty diff gears, carbon fiber shock towers, heavy duty diff output shafts, super chassis, good selection of pinion/spur gears, spring selection. These are what I have on mine and the best so far is the chassis and shock towers. Some alloy might be a good thing on mine. The arms are SO soft that if I use stiff springs the arms flex before the shocks compress, and the hubs/knuckles twist so much that setting toe/camber is pointless, useless soft plastic. Maybe someone makes stiffer arms from carbon/graphite composite? The steering knuckles are to soft as well, the screws holding them to the c-hubs can and do pull right out causing the loss of the bushing in the c-hub, so maybe alloy will help here increasing durability. The alloy steering bellcrank with bearings assembly is not a bad idea because the squishy soft stock one soon develops a bit of slop, and the extra weight is set down low on the chassis so it may actually improve handling by lowering the center of gravity. Any extra weight set down low can be offset by lightweight components higher up. Like c/f shock towers, and c/f upper deck. This is the route I want to go because the plastic upper deck offers no stiffening to the chassis that I can tell. If I take it in my hands and lightly flex car back and forth I can see the plastic upper deck bending like a peice of rubber. Also if they are not included, turnbuckles are a worthy option, and cheap. Also a carbon break disk, my stock plastic one melted in 5 tanks. Basically stock I hate this car! The stock chassis bends like a willow in the wind, the diffs leak all but the thickest fluid, the dogbones snap like pretzels, the plastic is WAY to soft...other than that I like it.