How to extend a tapered surface

there is a model that i have been working on that has a tapered profile however, i would like to extend a surface from the model that follows the nature of the taper exactly. i have tried extruding the surface then using the taper tool, however, due to the unique shape of the model, during the process the extruded body becomes distorted and no matter how i try it, i can never seem to match the tapered profile exactly.

i have also tried the extrudesrftaperd command but for some reason, the command will not run correctly on the model.

can somebody tell me the procedure and the commands needed to fulfil this operation. thanks

Hi Footy - as always, a file with your objects in it and some indication of what it is you’d like to do would be a huge help in sorting out what it is you are after.