Challah issues...

Twice when I baked a loaf of challah bread with some sort of dried fruit (raisins, dried blueberries, etc) I ended up with an under baked spot somewhere in the middle. My other loaves turned out fine, so I'm assuming that I added too much of the dried fruit. I added a 6 oz package of dried blueberries in this loaf.
So for the next loaf, I followed the same recipe and only added 2 oz of dried fruit (in this case, golden raisins and cherries). For a bit of a change I did a quick braid with the dough and laid a strip across the top, just to see how it proofs and bakes.
I have to admit, the strip across the top didn't do much for the aesthetics of this loaf, but it baked fine. The loaf turned out much better, but there was still a tiny spot that just wasn't baked quite as well as it should be. So I just upped the cooking time for a full loaf like by 5 minutes to 40 minutes total, and it turned out fine. I don't think the presence of the raisins affected it quite as much as the sheer mass of dough that had to be baked. Smaller loaves or wreaths require less baking because the heat has less to go through.