its not the hight but the cut. if u do dh u know u can use ruts not only as berms but good ones that u can hall ass through. small berms work as long as they r cut in the ground and have sharp edges so u can lean like f*ck and make ur bars almos hit the ground. so kid cut ur berm into the ground and the dirt u get from digging it out use to build the above ground part and have the top of them be at least vert, then u will be able to build strong sharp berms that can be small or big but no matter what they will not only work but work well