I have found the following functions in SDLUtils:

SDL_ScaleSurfaceRect
SDL_Stretch8
SDL_ZoomSurface

The ScaleSurface uses Stretch8.

ZoomSurface does Pixel level gets and puts. The Stretch seems to do row by row manipulation.

I'll try get a StretchDraw function working in S2DL for doing this. (May be more efficient to size the entire image surface and then use when/if needed)