does the chassis/vin plate have to be in a specific location ?

Yes

Off side front chassis rail seam welded all round or stamped on the rail, but that will bend it (some have it engraved). It must be easily visible by a tester. I put on three, one alloy plate from Sylva Autokits on the bulkhead (pop rivets), one on the near side (pedal box) and one on the offside chassis rail (belt, braces and elastic)

The stamped vin number needs to be on the drivers side of the chassis. Whereas the vin plate can (i think) be positioned anywhere but most, including me, choose somewhere on the scuttle/ bulkhead.

Mark.

I stamped mine by stenciling the letters onto the tube and then centre popping along the shape of the letters/numbers. Not as quick as stamping but much less likely to damage the tube.