As i understand it chrome plating a chassis...
if you get a scratch in the chrome it could cause it to create a stress risor crack in the chromolly? similar to the phenomenon in glass

as to the jig..and powder coating...we saw this happen...My chassis guy built Panoz race car chassis for a while and they had issues with fitment of parts after powder coating..
things like radiator mounting brackets and even
suspension support members..and light or small tube brackets that where body supports..
often they would be way off..when it came time to mount the hardware..
he had to make temporary jig bars to keep these parts from moving during powder coating ..
fwiw.

long tubes with lots of little welded do-dads seem to move the most...