You may see a 1 or 2 HP difference, but the main gain is in torque. The trick is you do not want to relieve the deck area at the cylinder bore when popping up 0.125" otherwise you will expose the top ring, your reliefs may be a little steeper than you would have wanted but if you leave the deck area at the cylinder bore alone you should be fine, but you need to know how much has been shaved off when you have the deck trued up. This is key to know how much you can get away with when popping up the piston out of the cylinder, some Kohler blocks may not be able to pop up 0.125" but 0.0625" or 0.09375" is better than none in my opinion. I have been using Arias pistons in my motors for the past 20 years or so, but am planning on using a different piston this year. I talked with an individual who had changed from a 0.0625" to 0.125" pop up in a Kohler block motor in 1991, at that time he gained 2 hp, but also gained 5 ft/lbs. of torque. Most individuals will build it one way then leave it that way till they either sell the engine or build something different, that was one instance where I seen a side by side comparison.Ever since the aftermarket blocks came on the market I haven't heard of too many that were not popped up 0.125".