It is an externally balanced engine so I'd expect some added weight but wasn't expecting that much!
I'm just deciding what to do now ,weather to get an aftermarket crankshaft with internal balancing or have my crankshaft balanced by adding heavy metal slugs but they are expensive...........
Follow the advice from Colin Chapman "Simplify then add lightness".
In your case remove the extra bits before they fly off themselves then drill big holes to remove any spare metal / weight that isn't needed
Do it in stages as it looks like somebody has already tried to do similar ...
Nice project, keep up the good work and keep the updates coming