Sergey;
VERY cool! I've been curious as to how these kits come out and what they look like once built... very interesting. The more so as I seem unable to get out of WWII armor! But a guy can dream, right?
A couple of comments: Adding those spare wheels is pretty nice - but you should probably make sure that 1) you make all those straps very straight and tight... thos wheels are heavy objects and straps which hold them on need to be tight - your's look a bit loose. And 2) - you have a very clear picture of what the spare-wheel attachment looks like on the turret - only a 3-way tie-down. Maybe this should be fixed up for best appearance?
I think you probably hit the near-right size with your reduced - size stretcher - I would suppose that this item would be around 2m long by proportionately narrow (maybe 0.7 or so m wide?) - so scaling it should be pretty easy. A 2.0m long stretcher should be about 57mm long? I don't know what the actual sizes are for your item - looks "OK" relative to the vehicle, but not knowing vehicle and stretcher size makes that all a guess. It would, IMO, look quite cool with the stretcher hung on the side like that.
I would suggest also making it thinner- the cut-outs show what appears to be pretty thick plastic. If you can sand it down a little it will look thinner and maybe more proportional to the real thing?
Just my opines and some suggestions. Your build looks pretty nice from here!
It's going to be paint-time soon! I'll be waiting to see what happens then!
Bob