Operation Teutonic Knight - Part 1

I liked doing basic conversions way back when I played 40k, and looking back I realized that it was because GW made their models very conversion friendly. Models were separated into distinct, simple, often plastic parts that made swaps possible even for a complete amateur. When I got back into wargaming with Warmachine and then Infinity, I found that although the models looked nice, it was very difficult to do conversions because they almost always involved chopping up a pewter mini and then sculpting detail back on.

Doing that with Infinity's scale is basically impossible with my skill level. I have enough trouble filling in the tiny gaps between joints, and any cut I make will not be clean enough. However, this time I think I've found models that are assembled in a simple enough manner that I can finally do an Infinity conversion: Teutonic Knights.

Both the Combi Rifle and Spitfire model are assembled in roughly the same way: Body, two separate arms, antennae. The arms do not ever join together, meaning that I don't have to deal with an extra hand stuck to a gun or whatever, and can thus do the classic arm swap.

The complication is that the arms are designed to attach at a specific angle, not flat like a Space Marine. To further complicate matters, there are gaps in the chest of one of them, because the arms sort of cross over his chest and these are the grooves for them.

The parts after cleaning but before any conversion work.

The plan is as follows:
-Drill out some of the arm sockets to make room for new arms angling in.
-Pin the arms. I wouldn't normally do this on such large arms, but I'm not attaching them "properly".
-Resculpt gaps between the arms and bodies, arm sections that would have previously been concealed, and of course the large holes in the chest.

The first two steps should be simple enough, but that last one is daunting. I'm mostly concerned about getting that smooth join between the Green Stuff and pewter. Any line at all will be noticeable and ruin the effect. Pulling this off will be a huge boost to my confidence, but messing it up will be devastating.