I have a very short update, but this one step changed a lot regarding my Eduard 190s!
First things first: I got my Qusickboost gun access panels today:
There's nothing special about them at all. They are basically a resin copy of the kit parts with some minor modifications: They have no detailed bottom and are very thin at the rear end to make them fit the wings without surgery. Anothe "modification" is the size. The resin parts a just a tiny bit smaller than the kit parts (probably because of the resin shrinking as it dries)
Comparison with the kit part:
I'd never thought about ordering them if I hadn't destroyed one of my plastic parts by accident. I can't use them on my A-8/R2 either because they require different gun bay inserts on the wings - those without detail and that "spacer" to glue the hatches on (Eduard's A-8/R2 is their only kit with the instructions not mentioning this 
) I simply robbed the plastic hatches from my 2nd A-8/R2 kit and I'll use the resin parts on that one (the gun bays are not in place on that one yet, so the AM parts will fit)
I'm writing way too much again... 
Now to the real update:
I FOUND THE SOLUTION!!!!
And with solution I meant the proper way of installing the gun covers. Eduard tells you to cut out a part of the wing to fit them. I simply ignored that step and came up with something different: I looked at the Quickboost parts and had an idea. All you have to do to get the hatches to fit without major surgery is to sand down ALL the surface detail of the gun hatch bottoms. jsut try to get them as thin as possible and they should fit the wing without any issues.
Before:
After:
The wing WITHOUT surgery (i originally planned on leaving this hatch open, but the wing was badly molded, so i had to "fix" it with a few layers of plastic sheet):
Gun cover in place. It fits almost perfectly with only a slight gap at the front edge (a very thin plastic strip should do the trick here):
You might notice the rather large step at the rear end of the wing root. This is caused by me sanding away a raised panel in this area while repairing the wing. I'll add that panel again after glueing the fuselage and wings together, so the step will disappear.
And the other side (I followed the Eduard instructions on this side):
Thae dark edge around the cover is no gap, just some paint remnants.
I hope this is of any help to those building an Eduard 190.
Cheers, Clemens