2.5” is too wide for 99% and encourages a fire hydrant shape. Some of us wish they had 2.125” tubes and 2.375” tubes.
If your cock is well lubricated, it will stretch out in the length direction slowly as it remains in the tube after packing. It burrows forward slowly like an earth worm. Enough time stretching in the length direction say 1-2 hrs and you will feel a soreness in the internal core of the penis, showing that it was effectively stretched out.
Without having the tube force it forward the cock will prefer to grow in the girth direction at the expense of length.
The cock is like a long stretchy balloon which only has so much stretch and stretching too wide limits some of the stretch in the length direction, conversely stretching too long limits the amount of stretch available in the girth direction.
Many of us wish it was endless growth, but those of us who have been at it for 5 or more years find gains do plateu.