Quintus tower has a reversed L-shaped base. There is a back ignision point of secundus tower.
Quintus's nature is similar to quartus tower. Its steps are like staircase.
Basic set up is started by for example AA AB.
You can also set up by AA AA AB.
It is one of strong point to use all ignision colors. (In pic it is red)
3rd set point
From left, red double, green double, others double
Others sets
These are your prefarable which it is better. I use left one but right one seems to be majority.
Trick of Quintus Tower
(If ignision point is right) Quintus tower may have a very high axis (3 column) cause of using all puyos.
It is bad shape of high axis and low its side. Cutting is one solution of them problem.
Converting to other chains
Quintus tower is rarely converted to other shape. Usually looking only tower is better than agressive converting.
Of course by miss setting and Opponent's rush attack, you have to convert to.
Here are converting examples.
Reference:TAK's Death Tower Blog (JP)