Stormtroopers have it rather bad when it comes to dual-aptitudes. As a support specialty they also get less starting XP, and I figured the starting kit was the reason for this.
As it is with the changes, the average stormtrooper would be just right [although at his limit more or less] with a total SB+TB of 7.
By the table, modern day soldiers wearing full kit and body armor are looking at around 38kg as well.
Overall, I'm thinking the table is just a tiny bit too harsh: if you modify the table a little so that total 6 gives you that 45kg maximum, then the hellgun and armor plus normal kit oughta come out just right.