The program 3dMEMA is designed to consider both the point estimate and its associated uncertainty, which is embedded in the t-statistic value. Essentially, it means that individuals with less reliable estimates due to a small number of trials aren't artificially removed from the analysis but rather receive less weight in the model.
If you prefer to use 3dLME and want to remove effect estimates with fewer trials, I recommend replacing:
-ranEff '~1+Cond' \
with:
-ranEff '~1' \
As an additional note, you might find 3dLMEr more flexible, as discussed in this blog post. 3dLME will be gradually phased out.
Gang