I think you should be good. I have used Beman 340's with several Hoyts over the past EEK!, 30 years, and the 340's have worked at my 29" DL with everything from Hoyt 70lb Supertec, (330fps rating), to my current 60lb Hoyt Spyder Turbo, point weights 100gr to 125gr. The dynamic spine of the Beman and Gold Tip 340's is very wide. My hunting buddy used them at 78lbs with a couple different bows with the same weight heads.
Peak weight isn't a perfect indicator in all cases. The force on the shaft is variable depending on where maximum acceleration occurs. If it's all on the point of release end, the acceleration is greater than a peak force in the middle of the power cycle with respect to the dynamic response from the shaft. I don't think the Powermax will be a problem. One of the 350 rated bows probably would be.
