Grob102 elevator balance mods

Hi
The elevator balance mandatory mods weigh about 2kg. Thus you would need about
10kg in the nose to balance it. Now my understanding is that if you put weights
on the ends of a long fuselage and spin it there is a tendancy for it to end up
in a flat spin? please correct me if I have this wrong.

Also if all this weight is added to the glider and the AUW not increased it
would reduce the available cockpit load by 12kg? So we end up with a 'Safe'
glider very few are light enough to fly! Which prat used the latest mass
balance requirements on a 30 year old design?

Nigel