I am building the tripe from Sands plans and he includes a sheet on constructing the Spandaus but they do lack quite a bit of detail - don't get me wrong, they are good as far as constructing a basic replica goes but I want to try for as much detail as I can stand.
A couple of years ago, I acquired a set of Ray Holling's full size Spandau drawings from the San Diego Aerospace Museum. I believe he drew these in the early 70's. They are packed with detail down to all markings and proofmarks but are not necessarily construction drawings but more schematic. You could probably build a working gun from these but the Gov't. would probably frown on that ! They tend to be pretty picky about who they let fly armed aircraft !
I think you can even see these drawings on the wall over my work bench in a couple of the photos I have posted here. If I remember correctly, the three sheet set cost about $ 45.00. They are approximately 1.5' X 5'. A call to the museum archival department would be a step in the right direction if you wanted to get a set ( they are pretty interesting to look at ). Sorry but I don't remember exactly who I spoke with - do remember them being very friendly though !
Around this same time a couple of years ago, I was in Arizona and made it a point to stop at the Champlin Museum. The curators were kind enough to actually remove an LMG 08/15 from display and allow me to photograph it from every conceivable angle. They were extra helpful and I still thank them !
To sum it up, I suppose I am trying to construct the guns using all of these sources. Sands has some good construction points, the Holling's drawings are dripping with detail and my photos allow me to see the real thing. I don't know how mine will turn out but hopefully they will look the part !