RV,
I'd disagree with your friend. At least on being able to shoot a Mare's Leg more accurately than a conventional handgun.
"Holding it roughly where a conventional stock would put it" can be taken two ways.
The first would be resting the stock nub against the shoulder for something resembling "normal" sighted levergun fire. Can be done, extremely awkward & inefficient. The Rossi has an extra inch of nub that makes it slightly less awkward, but I can't fire either brand with any comfort at all that way.
The second would be holding it with the receiver near the face (or against it), forward and independent of any stock to shoulder contact, and using the sights. With any cartridge of .44 Mag or .30-30 recoil levels, you do not want to be holding the gun back anywhere near your face with nothing to stop its rearward motion under recoil but your arms. It WILL cause pain, if not on said face then it'll almost certainly strike the shoulder.
Ghost ring apertures work best the closer to the eye you can get 'em, and again- you don't want that gun anywhere near your face in a heavy recoiling caliber, supported only by your bent arms.
My Chiappa with a 200-grain lead bullet at slightly over 900 FPS in .44-40 (a mild load) almost took out a lip when I was first exploring possibilities with the thing.
I can make it work at distance, but it's slow & cumbersome. I can do better, quicker, with a conventional handgun.
In my opinion, the prohibition against sawed-offs wasn't because they were necessarily more effective, but largely because they were just so easily concealed (in the clothing of the 1930s).
Stockless leverguns are just not that efficient, were not the primary "target" of the 1934 NFA, and just got lumped in with other weapons that were considered more important to prohibit (and/or more commonly used in criminal endeavors).
The Thompsons and shotguns were more efficient (at short ranges) in either stockless or short-barreled form, but weren't as dependent on precise aiming.
I'd question how often Clyde Barrow carefully aimed his BAR whippet, with cut-down stock, as opposed to hip firing (or possibly under-arm firing).
I had an idea of possibly using an ML for serious purposes, and that's why I did explore various ways & positions to shoot it.
I found that it's possible to build some fair hip-shooting skills, at short distances. Accuracy in so doing is far inferior to what I can do with a conventional handgun & sighted fire.
I can hit a steel target two feet tall by three feet wide at 75 yards with my .44-40, freestanding. I can do the same with several revolvers and pistols I own, and faster without having to lose the firing grip & sight picture, and cycle the lever.
It does better at distances by using a two-handed hold on the gun's wrist than by trying to hold it with the fore & aft rifle hold we'd normally use.
It's heavy. It's slow to fire successive shots. It should be kept away from the face, with any recoil at all.
It CAN be forced to do certain things, but it's harder on most of them than with a good revolver using a 6-inch barrel to achieve decent velocities in a given caliber.
I wonder if your friend has ever actually worked with an ML.
The .30-30 has a very limited mag capacity, a .45-70 ditto, plus recoil that can cause serious injury in a stockless levergun if not VERY carefully held.
I do concur that the Mare's Leg would make a jim dandy club.
Denis