As you most certainly know, the Mormon apologists cannot adequately answer the criticisms of The Book of Abraham. For example, in an article (previously on the BYU site and linked from here) with the title "Criticisms of Joseph Smith and the Book of Abraham", there is a very weak rebuttal to the charge that Joseph Smith filled in portions of Facsimile No. 2 with nonsense material (copied figures from the book of breathings scraps).
"Smith gave instruction to his woodcut artist on the missing portions of Facsimile No. 2, evidently telling him to insert some characters for the sake of aesthetics (footnote 57) But Smith made no attempt to interpret those characters on the facsimile, which he certainly would have done if he was as daring and/or as stupid as his critics style him (footnote 58)"A problem with the Joseph Smith/Hedlock Facsimile 1 restoration is that the figure holding the knife is facing the wrong way. When one looks at Papyrus Joseph Smith 1, one notes:
1. The left leg of the standing figure is forward. This is confirmed by the
line between the two upper legs.
2. Because the left leg is forward, the figure's frontal view is visible. Also, the arm extended over the figure lying on the lion couch is the left arm.
3. The lower part of the standing figure's right arm appears to be hidden behind the right leg of the reclining figure.
In the Joseph Smith/Hedlock reconstruction, this is all reversed:
1. The right arm (holding the knife) is extended over the reclining figure.
2. The back of the standing figure is visible.
3. The other arm is not shown.
Charles Larson's reconstruction in ...By His Own Hand Upon Papyrus, has the standing figure facing the proper way (front). However, he does not point out that the figure in the Joseph Smith/Hedlock reconstruction is facing the wrong way. Also, I have never seen this inconsistency pointed out in the limited amount of material I have read about the Book of Abraham.
One final point; if the scribes were practicing, why did they use Papyrus Joseph Smith XI as the source of the Egyptian characters? Why didn't they use the "Missing Black and Red Scroll" as a character source? That is the one that some Mormon apologists claim Joseph Smith translated. However scholars, who are not apologists, have good reason to believe that papyrus never existed and the 'missing' scroll containing red is likely the recovered Papyrus Joseph Smith VI or another one of the recovered scrolls containing red.
Also see Chapter 3 in Quest for the Gold Plates and Seymour's subsequent look at the material.