You can always build a simple vacuum forming machine and make some more accurate blisters. Maybe make them just slightly oversized to go over the existing ones.
I understand about a particular out of scale issue with some aircraft. I cannot stand to see the long cowl/noses on the Fokker DR1 triplane. I went to great pains to make my 2 tripes more scale in this area.
I guess my point is when it comes to ARF's, you have to lower the expectations and live with it, or modify/fix them if you cannot. For the price of these things, I do not think you can ever expect them to be exactly what you want.