5.9 Magnum flywheel - DIY with bolt-on weight??

I purchased a 5.9 flywheel and decided to measure the balancing holes. Here's the math I've done with the result.

Weight of cast iron is 0.265 lb/cubic inch x 16 = 4.24 oz per cubic inch.

1 cubic inch = 16.387 cc

The balance hole volume is 18 cc / 16.387 = 1.098 cubic inches

1.098 x 4.24 = 4.65 oz. at 3.9"

Center of flywheel to center of holes measured using a caliper = 3.90" I suspect the intended measurement is 3.88", the same as the LA 360 but I will use my measurement.

4.65 oz x 3.9" = 18.13 inch oz.

This is much closer to the LA flywheel which has a known balance of 5.1 oz at 3.88" = 19.79 inch oz.

There is a shallow drill spot closer to the outside with a volume of about 0.2 cc. I suspect this is a final balance adjustment. There is an angled hole through the thinner center portion that has a volume of about 0.3 cc.

I doubt these are significant. In my view the 3 large holes are what make up the balance specification. I'll post some pics tomorrow.

A couple more bits of data: the holes measure 1.043" diameter and 0.660 depth. I added a pic showing the drill bit angle (I get 30 degrees).