"He who marches out of step hears another drum." ~ Ken Kesey
Define "discoloration".Do you mean bleed or yellowing of the ink due to high heat?What are you using to make your mix now? You may have an equivalent already listed.Why not cut the ELT-S? I dont understand making sure its safe for "ELT"...
Double check cure temp for Quick White.
i don't know if this would transfer over well, but what i do with matsui waterbase for vintage white is 2 parts clear to 3 parts white. you could always try mixing up a little bit of that ratio with the soft hand and mixing base just to see if it works.
...usually a request for "vintage white" is like landing on Free Parking in Monopoly, as it usually grants a lot of leeway and makes the job easier.