For the reasons you describe (which I mostly agree with), I do not ever use
'asymmetrical playtesting' unless that method is unavoidable.  However,
you should know that I used many permutations of positions within my
'missing pieces' test games to try to average-out positions that may
have pre-set a significant positional advantage for either player.  

Yes, the fact that SMIRF currently uses your (Scharnagl) material values
with a 'normal, average' material value for the archbishop instead of a
'very high' material value (as well as the interrelated positional value
given to the archbishop with SMIRF) means that both players will place
greater effort than I think is appropriate into avoiding being forced into
disadvantageous exchanges where they would trade their chancellor or queen
for the archbishop of the opponent.  Still, the order of your material
values for CRC pieces agrees with the Muller model (although an
archbishop-chancellor exchange is considered only slightly harmful to the
chancellor player under his model).  So, I think tests using SMIRF are
meaningful even if I disagree substantially with the material value for
one piece within your model (i.e., the archbishop).

Due to apprehension over boring my audience with irrelevant details, I did
not even mention within my previous post that I also invented a variety of
10 x 8 test games using the 10 x 8 editor available in SMIRF that were
unrelated to CRC.  

For example, one game consisted of 1 king & 10 pawns per player with 9
archbishops for one player and 8 chancellors or queens for another player.
 Under the Muller model, the player with the 9 archbishops had a
significant material advantage.  Under the Scharnagl model, the player
with the 8 chancellors or 8 queens had a significant material advantage. 
The player with the 9 archbishops won every game.

For example, one game consisted of 1 king & 20 pawns per player with 9
archbishops for one player and 8 chancellors or queens for another player.
 Under the Muller model, the player with the 9 archbishops had a
significant material advantage.  Under the Scharnagl model, the player
with the 8 chancellors or 8 queens had a significant material advantage. 
The player with the 9 archbishops won every game.

For example, one game consisted of 1 king & 10 pawns per player with 18
archbishops for one player and 16 chancellors or queens for another
player.  Under the Muller model, the player with the 18 archbishops had a
significant material advantage.  Under the Scharnagl model, the player
with the 16 chancellors or 16 queens had a significant material advantage.
 The player with the 18 archbishops won every game.

I have seen it demonstrated many times how resilient positionally the
archbishop is against the chancellor and/or the queen in virtually any
game you can create using SMIRF with a 10 x 8 board and a CRC piece set.

When Muller assures us that he is responsibly using statistical methods
similar to those employeed by Larry Kaufmann, a widely-respected
researcher of Chess piece values, I think we should take his word for it. 
Of course, I remain concerned about the reliability of his stats generated
via using fast time controls.  However, it has now been proven to me that
his method is at least sensitive enough to detect 'elephants' (i.e.,
large discrepancies in material values) such as exist between contrasting
CRC models for the archbishop even if it is not sensitive enough to detect
'mice' (i.e., small discrepancies in material values) so to speak.