I would like to see his guidelines. His work is awesome because you can instantly tell what unit it is, yet you can also see his own flare in it. Seeing as how this is mainly for practice, I haven't drawn out this whole guideline I'm gonna follow for any units I model.
Start with the original cavedog unit, or work from the Cinema renders for Total Annihilation or snipits of the Cinema movie.
Import the ingame models into upspring, the export them as .3ds or .obj, I've had the best luck using .obj though and then open them up in your modeling program, and work from it that way.
It may just be my opinion, but the OTA units are so well refined and even for being what.. 10+ years old, they are in all regards a perfect set of units.
The only drawback to the OTA content is that all models Cinema and ingame were textured using a square tileset, and not by unique uvwmapped textures.
If you're going for the classic TA look, original content is where you start it off, anything else is free territory limited only by your imagination.
As for this hammer model, Argh's latest screen shots looked great. The only thing that doesn't look great is the way that the barrel covers open.
Personally I would suggest that the bottom cover is removed entirely and the metal barrel cap is appended to the top cover instead. This would give protection to the front and top, while leaving the bottom exposed (not many things are going to shoot upwards from below a small T1 unit anyway), and I think it'd look far better to just have one cover flipping up... possibly telescoping in on itself at the same time to become shorter...
Otherwise the bottom cover could be left but with the cap on the top cover, flipping the top up would allow the barrel to fire without the bottom moving. At present, it is technically only necessary for the bottom cover to move, this would just be a case of inverting the covers.
I like how the top cannon part came out, though I seem to recall that the Hammer seems to open up the ends of the cannon when it fires? So I guess I'd have to split it in half. Also the feet are weird, I gotta work on that too. Let me know what you think!
Good work so far but I have to say something about that very first model. I expect Mario and Luigi to pop out of those cannons at any moment.