It is fairly clear which of the fly serpin folds are likely to be non-inhibitory from the hinge sequence concensus, so I suggest that these should be flagged under: Protein features are: Serpin domain; Serpin family, putative non-inhibitory serpin fold.
The putative non-inhibitory serpins are:
Spn28Db
Spn31A
Spn43Ab
Spn43Ad
Spn47C
Spn53F
Spn75F
Spn76A
Spn77Bb
Spn77Bc
There are also two modified serpin fold which include large inserted segments, Spn100 and Spn85F, which should be similarly flagged as serpin-related fold with an inserted segment, or some such. 
CG14470 should also be flagged as being a large protein which includes a serpin fold domain, this is an oddity, but there are orthologue in other insects.
David Gubb
CIC bioGUNE