This was a conversion I did many moons ago for my old Demonhunters army. I made it, and a few other pieces of a similar nature, not long after that first massively converted squad of Grey Knight terminators that won the Gold at GD.
I was taking regular Space Marine bodies and converting them into terminators, since all the was available at the time was the old metal versions.
This project really taught me the differences in the properties of green stuff and brown stuff. Each one has a very different purpose.
Brown stuff holds an edge very well, but it can be very brittle. Green stuff is more flexible, but it has a 'memory', which makes it less viable for other things. I have learned a lot about green stuff since then, as well as Apoxy Sculpt.