thanks to everyone for your kind comments
I still have the other half of the train to build. There is sufficient space on the other track to accomodate the other half of the train.
Rather than build it as a standard BP-44 I decided to try something different with the "Kanonen & Flakwagen".
Sawodny's books mention that Wirbelwind turrets were used on some german armoured trains. Photos of these are rare, as its a late war feature. I have found 4 pictures in total, none of which is a very clear photograph, but clear enough to identify that these turrets were in use.
The armoured trains were built in Breslau (source Sawodny) and the Wirbelwind turrets were assembled in Breslau (source Schiffer), so the combining of Wirbelwind turrets with armoured trains was a practical measure. The Wirbelwind turrets were useful to provide more protection from small arms fire for the gunner & loaders than the rather exposed quad Flak 38s that are most commonly seen on BP-42 & BP-44 trains. All information is again from Wolfgang Sawodny's useful armoured train books.
One identified use of a Wirbelwind turret was on Panzerzug Number 65. This was one of the original six BP-42s started in 1942 & completed in early 1943. It was damaged in the Balkans in 1944, then repaired and sent to the Oder Front in February 1945. It was later withdrawn to protect the southern approaches of Berlin near Zossen. This train remained operational and fought on till the end in May 1945, when it was surrendered at Holthusen, in northern Germany. Possibly it picked up the Wirbelwind turret when the damaged train was repaired and refurbished in 1944. See pictures below.


Another picture that seems to show a Wirbelwid turret is Panzerzug Number 73. It was abandoned in May 1945 at Udine near the border of Yugoslavia, Austria and Italy. (see below picture)

I haven't put up pictures of the other Wirbelwind turrets on trains as they are of poorer quality.
To get the build underway I prepared the sides, ends and roof of the 'Kanonen & Flakwagen', which took a lot of sanding, as the plastic is moulded very thick, without angles at the joins. Its essential to do heavy sanding on the join edges to get the joins to match up, and they still require some additional filler and sanding afterwards.
I opened both top hatches in the radio/command area of the wagon, and cut out the entry/exit doors each side to make this wagon look more interesting & provide more opportunities to pose figures.

I also cut a hole in the deck where the Flak 38 usually sits to allow the turret to be inserted, and cut off the fold down sides that are on standard BP42 & BP44 flakwagens, as the pictures show that these were removed to allow the turret to freely rotate. I also built up the deck and covered it with Archer transfer anti slip tread.
The light grey spray is to highlight joins to check what areas need more filler, sanding & improvement.
The turret is test fit here, the flak barrels are not exactly parallel to each other




more will follow when more progress is done
cheers
Neil