my opinion's based on my reading and the few guys i've talked to about it (that take speed into account) don't feel comfy about using a hyper with a predicted mean piston speed of over 4000fps or so. A 340 at 7200 is still about 9% slower than the 4" stroke at 6500. At 6500 the mean piston speed is 4333fps in a 4" stroke. That's over 7100fps at peak piston speed. I love kb hypers - but there is a point that i get nervous about them and just feel safer with a forged piston.