I`ve got a Henrob/Cobra gas set and using the gun hand piece is fine although at first it seems big and awkward you soon adapt. Some of the bigger mig hand pieces are also quite bulky. I am sure you would adapt as the fusion process itself is taking place at a small distance from the tip.
I've got 1 too. A very capable piece of equipment that I've used to make all sorts of things with.
Something that tends to get a bit misunderstood about the Henrob/Cobra/DHC torches is that they are very different to a typical Oxy/Acetylene torch in that they give a much more focused flame with much lower gas velocity (they also cost heaps more in Aus...........). This lets them give more accurate welding work than a typical gas torch as well as be able to weld much thicker material. The low gas velocity allows you to bridge some pretty big gaps, too.
The other thing I like about them is that the weld is very ductile and has much less stress about it than a MIG weld does. This is easily seen by how much a piece will move when a corner is tacked. A typical MIG tack can pull considerably as the weld cools. With a Henrob tack, the piece will move much less.
I've only done small amounts of body welding with my torch, but I've made 2 turbo manifolds with it, welded up (yes welded, not brazed or soldered) )a hollow/water cooled copper bus bar and and high pressure hydraulic stainless steel lines (both for work), repaired a thin walled muffler or 2, seam welding in the engine bay of my 75 plus added chassis bracing. Made all sorts of exhausts and extractors. Mounting points, intercooler plumbing (in mild steel exhaust pipe), power steering lines. Used it to heat things to expand or bend them. Soldered copper tube.
Down sides are that you do have naked flames going places where you might not want them to go and the torch can be a bit bulky at times.
And I can't weld aluminium for ***** with it.............
So I just bought an AC/DC inverter TIG.