I think it would be unreal. I had a HD4 and I now have a Ripmo, but I think a HD4 mullet would be the best of both worlds for rowdy riding. The HD4 is way more progressive so takes the big hits better, while the Ripmo carries more speed over trail chatter. A 150mm 29er fork would be like a 170mm 650b fork which is how the enduro team run the HD4, and you'd gain the bigger wheel which wouldn't fall into as many holes.Anyone done it? LBS has a great deal on a frame with X2. Thinking 150mm 29er front for 150/150.