Hi Geena,
Since make_random_timing.py does not currently have the ability to control the basis function (aside from the length of the stimulus, which dictates GAM vs BLOCK), you could change GAM to MION(1) via sed or something, as in:
sed "s/GAM/'MION(1)'/g" cmd.3dd.OLD.txt > cmd.3dd.NEW.txt
That would change any instances of GAM into 'MION(1)' in the "OLD" script, and save it as a "NEW" version.
I can look into how straightforward it would be to add such a thing directly into make_random_timing.py, too.
- rick