here's the adjustment settings in flashprint:
flashprint adjust.jpg

Also why don't you just seperate the two pieces and print them further apart ?

In simplify 3d select the model, click MESH, Then SEPERATE CONNECTED SURFACES.
Nothing appears to happen, but if you look at the list of models loaded, you will see a new one. The two gears will now seperate and can be individually saved, deleted, moved, resized etc.

Amazing how useful that option is :-)

Size adjustment in simplify3d:
s3d-adjust.jpg