It involved grinding off the cast features and detail of the Mato M4A1 and replacing the curved lines with the straight lines of the welded rear half. This was done using plasti-card and Milliput two part putty. All the curved lines of the cast hull were sharpened up at the corners of the rear hull, deck and the rear panel, plus the rear panel was restyled with the 'U' shaped cut out of the early M4.
Milliput was then used to re-inforce the plasti-card and was sanded down where necessary; the welds can be added at the same stage. If you can do that, then the rest should be easy for you. It worked for me and the finished hull was fitted to a HL chassis using the Mato rear panel, although in hindsight, I might as well used the Mato bottom half. Hey, I'm new to this scale!
There was no need for the hessian camo, but being a Firefly it seemed the right thing to do although it obscures the applique armour and the body lines, but its all there where it should be