i see.. coz from the way my friend told me the shop like scolded him or sumkind cause he asked them for odd match-up of spring rates with the shop stressing out 6k & 4k is already soft enough..
must be some dungu fella.. i bet he doesn't know what are the stock spring rates of the car.
anyway.. tender & helper springs are two different types, although they look similar. tender springs are softer than main springs & may help with low speed dampening. helper/assist springs are a lot softer and fully crushable when the tires are on the ground. helper springs will keep the main springs intact under full droop.
tender springs may help on height adjustable only. for body shift design, you don't one. like others have suggested, better use lower spring rates for more comfort. knowing the car and the stock spring rates also help to determine requires stiffness.