Hi zig
The only way I can fathom this happening is to take Captivate
and record the larger. Then use the Project > Resize option to
reduce the size of the larger to match the smaller. Then import
that/those slide(s) into the smaller.
Or, you could go the other way around. Record at the larger,
leave it at that size, then import the smaller into the larger via
File > Import > Slides/Objects.
Cheers... Rick