Issac, can you explain what it is about a unison that will cause the tone to shorten?
Quicker decay, perhaps.
Yes , Chris, I (thanks Dan) think that when we say "tune the attack" it is not the attack per se that is empowered by the tuning, more the decay moment, the attack is then cleaned because energy is immediately given to a larger spectra, then, the power allowed immediately can be regulated by tuning the decay more or less "late" . The range of possibilities is not that large and depends of the differences in spectras, iH, voicing, (string lenght eveness in the unison , string quality and hammer quality)
You can strive to obtain much power immediately, or allow the attack to "enlarge" , this gIves more control on tone to the pianist. I believe that basically the playing hand that tells the brain when to tune (hence the possibility to tune with earplugs up to some point, as the thickening of tone is perceived)
The idea "hear 2 strings as it was one" is good as long as the string imagined is thickened and more present, more lively.
The tone can be explosive but at the beginning of the aftersound.
I have no other easy trick than to evaluate how the tone escapes and "tune the attack", but to do so we need to focus on coupling at a certain level, when adfing the 3 string straightness of tone can be balanced.
Tuning good intruments make this easier to perceive.
Then, voicing can be envisaged leaving more power at the attack.