Those links above are quite helpful mate so you should check em out, but what i would also say is your RB26 gonna be seeing some serious track time,Week end warrior or just a streeter on a hardcore race engine id say yes because at high engine load+high RPM the flywheel/clutch assembly not being balanced with the crank shaft and harmonic/Dampener assemblies will create Crankshaft wobble at high RPM/High speed/Engine load witch isn't a good thing. the RB26 is well known for decent crankshaft wobble at high RPM a harmonic dampener should be invested in after upgrading the oil delivery system in my opinion then the T25's, like it says in one of the articles you should get your pistons, conrods Big end and small end measured and balanced then you can properly balance the crankshaft and harmonic/dampener-Flywheel/clutch assemblies. on a weekend warrior id probably do it to just for piece of mind but if its just a streeter i wouldn't worry about it you wont generate enough High speed/High RPM/Engine loads to cause you problems . One thing to remember to is even though some thing is mass produce doesn't mean there all the same tolerances there is variation from kit to kit and there definitely not gonna be the same as whats in your car currently aslo due to ware on components Fraction of a gram counts when balancing a engine hope this helps you out mate