Dynamic Balacing
Bob, I have hard numbers for every balance I do and provide that data to every customer. I'm not quite as computer savy as our host DR or I would post the actual plots, but here are the numbers for Alex's 7 & 10.
RV7: 4 Runs: .132, .048, .025. .035
RV10: 3 Runs: .069, .009, .014
Alex's aircraft were somewhat unique for RV's as they both had custom flywheels to support air conditioning so I had to drill and install weights on the spinner bulkheads on both aircraft. As you can see from the above numbers the final run with the single weight installed increased by .01 IPS for the RV7 and .05 for the RV10 (sometimes it goes down but you never know until you check). The final position/weight is calculated from the 2 weights temporarily installed on the spinner screws. When you change the radius and move them aft to the bulkhead things will change. I strive to keep the final IPS number less than .04 and I know when I calculate a move to the bulkhead there is the possibility for some error so I work to get the number a bit lower to allow for this.
When you can use the Lycoming flywheel to install weights its easier and more accurate to split the weights on the flywheel and easier to tweak.
When installing on the bulkhead I prefer to calculate a single weight positiion so you only drill a single hole, but this will always be a bit of a compromise as there is no way to tweak it (if someone really wanted to tweak it as low as possible then you could drill 2 positions on the bulkhead and split the weights). However, in reality once the balance is in the .03 IPS range or less you really aren't gaining much to go to .02 IPS.
Keep in mind that most Prop shops that do balancing call it quits when they get to .1 IPS which is the industry "standard" upper limit after balancing. Being that I'm self employed, not in a hurry, enjoy doing this and pride myself in precision I'm not personally satisfied until I've taken the time and have done the best job possible which means I don't quit until I have gotten to at least
half the industry standard or less (usually less). My average balance generally ends up in the .025-.035 range but I do love it when I get them in the .014 range like we did on Alex's RV10