The mechanical quality of these intl-outdoor springs is actually quite poor (test , see also post #3), but since they only need to do a very minor travel they do the mechanical part of the job still very well. The electrical conductance however is superior to any other spring out there.
As far as availability goes: this spring is an exclusive intl-outdoor project (Hank had them especially made) and can not be found anywhere else. So Hank is the person to contact if these springs are to be used. And I surely do recommend them for the FW3A !!!