I don't understand the discussion of oblique nibs. It sounds as though line variation may be expected from the obliqueness of the nib. Line variation comes from nibs that are stubbed, italicized, or flexible, not from being oblique. Oblique merely rolls the nib to one side. The three nib types that give line variation will produce the wider line descending. With an oblique, the wider line will be on a diagonal to the side the nib is canted. if a nib is round, the line will be uniform. If a round nib is oblique, it will still give a uniform line. It will do it, however, with the nib canted.
Correct. But as the cant tô one side is different than my normal nibs, it changes the appearance of my writing somewhat. Especially with the OBB. So: when going up in size from a M to B then BB, rather than just a circle swelling in size/forth evenly, it now develops an oblong shape (unrelated to the "oblique-ness," Just due to size). With the angling tô one side that is an Oblique, the angle of attack to the paper changed as well. Rather than the nib producing a wider line on a downstroke perpendicular to the base line and a narrow cross-stroke parallel to the base line, it produces (in this case) a narrow stroke of an obtuse angle to the line (ex, lower left to upper right) and a wider written line at an acute angle to the base line (upper left to lower right). Assuming that I'm not changing the way I'm writing, but simply rotating the pen/nib in my normal grip to better suit this nib then it changes the result slightly.
Ex: In this case I experience more width on cross strokes rather than as usual on down strokes. Curves widen at a slightly different place than normal.
These, however are just what I have noticed with the OBB nibs which may differ somewhat from others have experienced (or my interpretation of my observations may be incorrect). Also, as I mentioned I have adjusted the two OBB nibs' performance to better suit me (making wetter, adjusting relationship to feed) and have yet to use the other two. I can see the OM not changing much, but the OB may prove to be interesting for me.
Also of note, I very rarely write with the pen held so that the cross stroke from the nib is perfectly parallel to the base line I'm writing on. Most of the time holding my pen at something of an angle to the line, closer to that as I also tend to angle the paper as well. So my rotating the nib slightly may produce a more noticeable effect for me than for others.
Any further questions on this please PM me, as I do not wish to get further off topic in this thread. I very much enjoy seeing and reading about everyone's new additions/acquisitions.