Well bigger valves help the motor breath more in the tvt smaller stems and bigger valves will make a big difference. Breaking stock rockers is a fact of life. Just part of racing. Roller rockers on the other hand are made by only one person Charlie at ASEP. The new ones are relived unlike the old ones. They have broke. I have a set of unrelieved in a back up motor that has 4 years of hard racing and no problems. Pushrods bending well thats a fact of life with any motor. Let the lash get a little loose it try to spit it out but hair lips it bam you bend it. My Thunder Twin by Bertrand Hydraulics has 38 races since I have aquired it with only 3 motor DNF's. One I simply blew it up, the second one of those I broke one of those relieved rockers (it now has the older non relieved on it) the third I broke a push rod. Yea broke. I am having some made professionally now that will solve that issue. I hate the stock ones. But for the money its one of the best buys out there. 3500 for a turn key thunder twin. Where as most other motors you sink 35 in the motor alone. Plus the motor. Thats for a motor like I run. Steve Bertrand builder of the Thunder Twins can build one to meet the wallet size you have give him a call. 1-800-236-3611