Also remember, this is a layered manufacturing process. I know on my printer, that stresses work differently in the various axis (axis's?, axi?, axis?), ahem, directions. If you are putting a lateral stress across the layers, it may tend to delaminate (words are failing me tonight, that's poorly described). It really depends on the orientation of how you print it and how it is used and designed. The identical same design might fail catastrophically with minimal loads, but print it 90 degrees the other way, it can be a beast. Also, what may be rigid in one direction, might be flexible in another, and brittle in another, all relative to print orientation.

But it doesn't sound like you're putting a lot of stress on this frame (I've learned this through trial and error of supporting a 5kg load with 20kg lateral stresses on my racing boat parts), so I wouldn't worry too much about stresses. Because, if there are no other design considerations for the parts in question, again, why go with the smallest tolerance you can? Add a little redundancy to the design. Of course, if adding the 2mm to this part, makes you compromise another part, then it becomes an issue of priority.