I have no idea..but for the love of God please post up your Mentor Legion if you're doing them.
I used to have a really really old (read 25 years) White Dwarf magazine and it was back in the Rogue Trader days when they would list random chapters with special rules in the magazine. I fell in love with the Mentor Legion rules and background.
They had weird organization, and their coolest feature was a targetting-link, allowing multiple models to fire bolters at a single point, increasing the strength of the bolter by +1 for each additional strike. This allow a 5-10 man unit to combine bolter shots and take out vehicles etc.
Man...back when 40K was much more rich and interesting.