Bringing Cadimage cladding down over boundary joists

[Anonymous]

Hi,
I'm modelling a house on piles, joists etc.. I've used the wall accessories tool to clad the wall in weatherboards, However I'm then unsure how to make the cladding come down over the boundary joists + another 50mm as required. I've tried stretching but it won't let me? Any help here?
Also while you're at it you may aswell tell me the best solution for adding base boards to my model.

thanks.

Archicad 12, NZ

[Anonymous]

Screenshot attached

[Anonymous]

Thanks, It's been bugging me all day