<VV> Balancing

[Geoffrey Albert Clarke Johnson]

I Have a set of pistons and rods that I am balancing to put together.  On 
the pistons/rods, I have a 6 gram spread between some.  That is a lot of 
metal.  Is it possible to add a gram or so to one of the lighter rods so I 
dont have to remove  that much from others?  I mean doing this by MIG 
welding on a small bit to the area the needs it.  Somehow this seems wrong 
though, but could it be done?

Also as I recall GM balanced the piston/rod to its opposing piston/rod and 
not to the others i.e. in pairs.  Is this correct?  Can I do the same and 
not have to do as much metal removal? Will doing this result in an overall 
balance that is as good as balancing all to each other?

Please no take "take it to a machine shop and have them do it" answers. I 
like doing stuff like this myself, part of the point in playing with old 
cars.

Thanks
Geoff Johnson