I was using Oligoanalyzer3.1 to check the Hetero-Dimer, all the primer pairs produced by Primer3plus have some Hetero binding locus, sometimes 3 bases, sometimes 4 bases, and there is a "maximum delta G" index showing along with the hetero binding site. I'm just wondering what is the optimal index for "maximum delta G" and should the hetero bindings be strictly avoided? Is 2 or 3 bases binding acceptable?