Hi Lance, sorry not replying sooner.
Ref Strahles machine
Yes it did have the larger pump at one time at least as theres pics of it. But if you have the book I mentioned you'll see what I mean in both the pic of Strahle with it on P85 & the subsequent one of it wrecked on P86 you can clearly see what I mean. No airpump body but the round housing with the oil lines is there and central to spring rocker boxes. Maybe a relacement pump/engine retrofitted to keep her flying? who can say but one of those interesting connundrums to keep our minds active. 
Now onto von Sleich's A/C
I've scoured more, can't find a yes or no scrap of evidence though I have unearthed several other interesting features. A single reinforcing bar on the radiator for one as opposed to two in the kit. It also has a slide type of Radiator management shutter, crude rather like the Pfalz DIII kit one The flare rack needs scratching & the undercarriage axle fairing appears to be two tone Purple/green possibly? The Ogee gunsight seems to be a late addition & maybe If you have Windsocks DV/DVa at war book (I'm sure you do...lol) do you have an opinion on what the diamond square shape is above the tail on the bottom pic on page 33? Crude repair work maybe? Must have been a rather big hole to patch like this if it is.
Cheers Keith
Keith,
Your reply initiated quite a "frenzy" of page turning on my part; both issues are, as you say, the stuff to keep old minds active!
First, the question of which engine in Strale's 4594/17:
......... I agree that either / or is the logical answer. All the photos I have access to of the aircraft in it's early service when he flew it in Jasta 18 colours of blue/red with the axe motif clearly show a front mounted air pump. As you point out the photos of it late in his Jasta 57 service (re-finished in light blue with a red fuselage band) indicate no pump up front. I believe your interpretation of a retrofitted engine makes sense. I did find another photo on pg. 68 of Part 2 of the Osprey book that is of interest showing 4594/17 at Jasta 57 at Wasquehal Airfield in Feb 1918, still in his Jasta 18 colours and, if my mag. glass interpretation is correct, still with a pump at the front. It would have been at some time later before he wrote it off in May of that year that the engine would/could have been changed. I'd go with this scenario and build the engine with the rear pump.
As for the "diamonds" that question led me on a merry chase until I found the explanation I vaguely recalled seeing in the past..........if you have the WNW DV Instructions (I'm sure you do!) see page 12, Karl Schattauer's DV tail, with caption "the diamond shaped reinforcing plate on the fuselage in front of the tailplane, a feature not universally applied". I've seen many illustrations of these things, ALL on DV's but not on DVa's. I believe, when installed, there were two per side. I suggest a quick EMail to the Folks at WNW with a request for info and particularly their source/reference would be well recieved. (maybe Stephen Lawson as well?) WNW's were a great help to me in explaining/verifying their scheme for Montingen's black DV on their Jasta 18 DV Decal Sheet(30011)
If you do try it please share the results, I'd enjoy hearing more on the topic.
And now, back to the bench to continue with my "black monster" which at this rate should be finished just prior to my 95th Birthday (lol!!!!)
Cheers,
Lance