I'll try to not dig into this too deeply. But clearly, the krump can be done in many different ways, striking with the long or short edge or even the flat, against the opponent's flat or on top of his (short) edge, at his weak or strong, directly to the body, to the sword or as a bouncing strike first to the sword and then to the body.
Here is how Kal depicts the simplest version, stepping off to the right while cutting to the hands. Throwing your rear hand under your elbow protects it from the opponent's incoming cut and angles your blade so it cuts more or less at the same angle as the opponent.
http://daten.digitale-sammlungen.de/bsb00001840/image_136Talhoffer too shows it thrown diagonally forwards on top of the opponent's blade, completing it with what appears to be an oberhauw, but possibly also a short-edge unterhauw to the head:
http://daten.digitale-sammlungen.de/bsb00020451/image_23http://daten.digitale-sammlungen.de/bsb00020451/image_24Here are a couple of sources that can be mistaken for showing the ARMA interpretation:
The Berlin Sketchbook shows a few images that looks similar to the ARMA interpretation, but sidestepping diagonally forwards so you get an angle from which you can wind in a thrust on the outside with crossed arms is vital. This is what keeps you safe and enables you to pose a proper threat, as his blade is at your side, bound with your cross while your point is aimed at his balls or gut...
http://digital.staatsbibliothek-berlin.de/dms/werkansicht/?PPN=PPN614064619&PHYSID=PHYS_0021There are a few more similar images in that specific treatise. (Thanks Martin Fabian for putting my attention to it!)
It is quite similar to the counter for the "2nd" Zwerch shown in the Glasgow Fechtbuch (and described by several other masters, e.g Ringeck) where it is the
left fencer who makes the clever counter:
http://wiktenauer.com/images/6/68/E.1939.65.341_1r.jpgPossibly, this is also what we see on plate 84 in the Solothurner Fechtbuch. However, in that treatise we see the "regular" Krump from above to the hands on plate 88, identically to how Kal shows it.
The Rast fechtbuch again on plate 46r shows a similar stance that basically is a mutieren coming from a zornhau bind, where you through the pommel underneath your elbow which will wind your point over and inside the opponent's blade when done correctly.
As a sidenote, as he has been mentioned in this debate: Meyer says a few interesting things about the krump and has his very own perspective on it, but he is also aware of the older interpretations:
"So du Krumphauwft / fahr auff behend / Geschrenckt den ort wirff auff sein hend"
"Wann du ihm hauwest Krump zur sterck / Durchwendt / Uberlauff damit merck."
"Mit krump trit wol / wilt du versetzen / Das uberschrencken thüt ihn letzen"
Krump zun flechen wilt dich stercken / Wiet ihn schechst / solt fleissig merken"
"Merck so er dich mit Krump wolt irze & Bleib am Schwert & recht den krieg thu füren"
Unfortunately I don't have the time right now to debate more, but clearly there is not one single interpretetation of the Krump. The sources are quite clear on this. To me the krump is a simple cut: A cut with crooked arms that can go to the opponent's body or sword. What you do after that is a follow up, which can be winding and cutting, thrusting or wrenching.
ARMA's interpretation has some merit for the follow-ups, although I don't consider them actual part of the krump. The unterhauw would be fairly weak against a doublet and thus quite ineffective. A thrust would be better, which is what we appear to see in some treatises.