Shear stress distribution for a tapered beam

[gmreit]

TL;DR

Shear stress distribution tapered beam

I am reading a journal article from Balduzzi about shear stress recover on tapered beams. I can not get the exact constants he gets and I am stumped. Above is solving for differential piece of the beam. Equations 16-18 are the ones I am trying to calculate. I attached my work and the article.
Thanks!

 

[Daniel Boy]

Did you already get the constants?