Balancing Hoffman prop

[Old Koreelah]

I am in the process of balancing my wooden Hoffman prop. Static balancing it on blades shows the need for a mass weight on the side of the hub. There are six large plugs interspersed between the holt holes. Can anyone enlighten me as to their purpose, before I do something irreversible like drilling one out to see what's in there. I suspect they have a balancing function, and I'd rather adjust the mass there rather than inserting lumps of lead into the wood.

 

Nothing on the Hoffman site sheds any light on this. The prop's data placard reads as follows:

 

Gerate Nr. L-32.11/1

 

Baumuster: H011*-150 8 70L

 

Werk Nr.: 37829

 

Prufung: 38675-1

 

Datum: 11.10.77

 

Thanks in anticipation,

 

Lyle