Roadblocks: Every kit, it seems, has some "roadblocks" - stumbling points that can impede an otherwise smooth build. Some kits have more than others.
For the Tristar Flak 38 late, the top three (3) roadblocks, so far:
1. If installing the gun shields, hold off on installing the top shield supports until installing the shields. The instructions have you install them early. If you're lucky, they will align with the shield. If you're not, like me, you will have a problem. Because the supports are solidly glued to the frame, will have to cut them from their base, do a little surgery, and try to fit properly.
2. The gun sight link is attached w/o glue to a PE part then trapped in the gun so it can freely rotate. Seems like a nice idea but the attachment pin is very shallow. Against my better judgment, I tried this and, sure enough, the link came loose from the now-inaccessible PE part. So will have to try to glue in the approximately correct location. Best solution would be some sort of nut on the other side of the attachment point, but probably too shallow. Maybe just attach with white glue (?) before trapping. Good idea, perhaps, but falls down in execution.
3. This roadblock is specific to intended use as a portee on the krupp protze - while the Tamiya Flak 38 fits (barely), the Tristar Flak 38 does not. The Tristar gun base (or the supporting feet) is slightly wider than the Tamiya gun base - not by a lot, but by enough to prevent it from fitting straight into the back of the krupp protze. This roadblock could be fatal - at least to the intended use.
Some other notes - should insert the other half of the towing pin when attaching the ammo box to the sd ah 51 frame - easier to do before, but still possible afterwards. Also, for those allergic to PE, there are a number of very tiny PE parts that have to be no added.
Given roadblock #3 above, have decided to use the Flak 30 from the DML Sd.Kfz. 10/4 (1940) version. An initial build of the base shows that the Flak 30 base is much smaller than the Flak 38 base and so will easily fit. The 1940 version of the DML Sd.Kfz. 10/4 does not include a gun shield, only the 1939 version. A test fit of the Tristar Flak 38 base shows that it will fit on the Sd.Kfz. 10/4 supports for the Flak 30 so hopefully can use the Flak 38 on the Sd.Kfz. 10/4, though also will have to check the clearance with the side screens. Apparently, later versions of the Sd.Kfz. 10/4 were fitted with Flak 38s, so this hopefully is still reasonably historical.