Message:
>Is it ok to fabricate clamping blocks on the seat stays of my tandem {has no canti bosses)to adapt v-brakes?IF your tandem does not already have cantilever brake bosses, then I presume it is a steel frame AND quite old.
That being the case, the seat stays should certainly be sturdy enough for you to attach "blocks" which you might fabricate.
You will find that it will probably be cheaper & faster to either buy a pair of bosses which are subseqently brazed/welded onto the seat stays OR to cannibalize an old, non-suspended MTB fork for the bosses WITH some of the fork material which you can use to facilitate the attachment (i.e., keep the boss attached to a BAND which you will wrap & braze/weld/solder/glue onto the seat stay).
An alternative to attaching the cantilever bosses to the seat stays is to attach them to the BOTTOM of the chain stays (pointing downward).