With regard to the Ubi-GFP insertions, this is what I know:
The insertion on 3R does indeed map to polytene internal 83.  This is a
jump that I isolated myself from one of Ilan Davis' original lines.  I
told the lucky technician who mapped the jump not to bother defining the
map position beyond a numbered division.
I'm not so sure about the insertion(s) on 2L.  I isolated 1 jump myself at
36, and mapped two of Ilan's original lines to 33 and 38.  I made
recombinants of these insertions with FRT40 in various combinations, and
retained two lines, each with two insertions.  One line was 33+38 and the
other 36+38. And at one time I also had lines with only 1 Ubi-GFP 
insertion on the FRT40 chromosome.
I think I sent either 33+38 FRT40 or 36+38 FRT40 to David Bilder, but I
don't have any record of this.  If he doesn't know either, then the
information is lost.
I'll happily send you a line which has insertions in known positions!
I also have a line with an insertion on the X recombined with FRT18neo,
which is a natural partner to these other lines.  I don't know where the
insertion in this maps though...
I hope this is of help.
Best regards,
David Strutt
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Dr. David Strutt
Developmental Genetics Programme
University of Sheffield
Firth Court
Western Bank
Sheffield
S10 2TN
England