It's interesting you say that the recommended spring pressure is 350 lbs. If you look at the recommended spring on the Comp Cams website where the matching parts are shown, it shows open pressures of 450 lbs. I am using these rockers with their XR274R Street Solid Roller with 500 lbs. open and have not had any issues for at least 4 years now. However, I did banana groove the shafts for better oil distribution.