B737-200 and CRJ200 were BPKs first models. They both have transparencies like that. - 100 is the same mould as - 200,just shortened fuselage. I think guys at BPK realised it's not the best way to do it and changed the design. Newer design is easyer to instal and also better quality.
Thanks Ray! Welsh vacform is ok, but can't really compete with this. So, I added last pieces and this one is done. Photos are here viewtopic.php?f=14&t=3492