I've had tons of positive comments on my Tfex so I thought I would share how easy it was so others can make them.
Here's a couple pictures for reference. It's still not painted yet, I'm getting into 40 genestealers so he's a ways off to being finished.
It's super easy. I'll break it down for you now and take pictures when I get down to making my second.
#1. Using a carnifex kit, assemble the torso and legs.
#2. For the rupture cannon barrel, I used a plastic tube from the center of a cash regiester receipt tape. Paper or thermal doesn't matter. I cut out half of one end of the tube so it looked like a D. It was not a clean cut, I used pliers. I test fit the tube on the back of the carnifex model and kept removing plastic bits of the tube until it was a fit close enough that green stuff could smooth out the seam. I then glued it to the torso.
#3. Use green stuff to cover up the seam of the two parts. I blended the top armor plate to a point going up the barrel, most easily seen here
#4. I used 4 extra Trygon head shields around the end of the barrel.
#5. I used Trygon Prime mandibles under the barrel as supports/bio feeds.
#6. I used extra Trygon tail bits above the barrel for more bio feeds. I snipped off the tip and sculpted greenstuff veins onto the barrel that you can see in the above pic.
#7. I used extra armor plates from gant kits to create a string of armor along the top of the barrel from the torso armor to the Trygon head plates at the end of the barrel. This also helped the overall look and covered up some sloppy greenstuff lines.
That's it... It creates an intimidating Tfex at no cost if you have access to Trygon bits (I've purchased 3 Trygon kits so far so that was easy). Hope it helps all you Nid geeks.