Variations on an Allegheny

There are some variations on the Allegheny concept, prompted by my friend Frank's statement that he finds Triplexi fascinating.  But what, exactly, is a "triplex", I wondered.  Is it something like this?

or perhaps something like this?

Frank's verdict was that the first one (the 2-6-6-6-10 tractor) was just too awful for words, but that the second one (the 2-6-6-6-6) had potential.  Then Russ chimed in with the thought that, because of its size, it might need a hinged boiler, like some early 1900s Santa Fe engines had.  Personally, I don't see the need for any superfluous, extraneous hinged boiler:

I liked this one so much that I created a variant of it to use on my Christmas Card:

Russ pointed out to me that the penguins indicate that this shot was obviously taken on the little known Patagonia Extension of the Railway.

Finally, I decided to go Frank one better by making a Garratt Allegheny

Although I wonder if its 2-6-6-2+2-6-6-2 wheel arrangement really justifies the "Allegheny" part of the name.