Hi Canute.
Here is what a collector friend of mine sent me along with his comments.......
Hi, Rick
Maybe these might be helpful. You're right, there are FAR more Brescian pistols than long guns around. These examples should give him an idea of what would stylistically match a wheellock.
The color pic is of a piece I personally examined in the arms room of the Artillery Museum in Turin. Very odd piece, the lock with external spring looks very Silesian, and the sliding patchbox is unusual for southern Europe (barrel is rifled, too, which is also an oddity for the area.
On the more conventional examples, your buddy should remember that the polygonal butts were never as club-like as on Ottoman guns. They actually taper in thickness from the lock to the buttplate, as they flare outward in the vertical plane. Thus, my example is, at the extremity, 4 1/2 in. from heel to toe, and it's only 1 in. side-to-side.
Note the bottom-most piece on the page of line drawings, a schavezzo (folding stock gun). Does the butt area look familiar?
For shooting comfort I would prefer the polygonal style over the Arab-looking recurve of the Turin museum gun. They are actually quite ergonomic, I have no problem getting a firm hold and good sight picture with mine.
Also, your friend should keep in mind that Brescian fashion called for pin-fastening, not barrel bands. The iron buttplate actually forms a narrow rim around the extremity of the butt. And all the fittings are iron, during the wheellock era these guys had no use for brass (some Beretta-marked fowlers of the 18th cent. have brass trim but these have patilla locks and Madrid style fluted butts)..