The dovetail is , as you say, unusual in being 13mm rather than the more common 11mm.
It does create problems and unless you pay a fair amount for BKL mounts which can be obtained in 13mm then it is necessary to either use a mount which can be opened and tightened enough to fit , or to use split ring mounts.
The use of a conventional 11mm mount which just fits does push the scope off to one side but only by 1mm so adjusting the scope to counteract this is possible but needs to be redone for each new range as you are shooting at a very small offset angle.
With regard to reddot sights I have used the Hawke Red Dot Sport which has the split ring and this enables you to open the mount at both top and bottom enough to go over the 45' rail and to tighten adequately.
I'm sure others will have alternative suggestions but good luck with it.
I have a couple of photos and if I can find out how, I will add them but Gurgle the Hawke Red Dot Sport and you'll find photos.
Dagwood