I was just getting at the fact that the solder would provide more structural stability than a non-firm under chip injection or encapsulation would, which means it would add very little.
Firmer potting media has the disadvantage of typically having different thermal expansion/contraction characteristics than what is being fixtured.
Staking methods can work well, because there is typically a gap so expansion would not impose the same pressures/forces.
My can-it suggestion works well, because the interface media is thin (