I was using a slightly different calculation, but we seem to have come to the same result.

My calculation was based on the check-in/bag drop deadline. I was guessing - without looking it up - that check-in would close about 50-60 minutes before departure.

I have since determined that it is 60 minutes, so even a 15 minute delay could be problematic unless the OP's baggage appears very promptly (in my - limited - experience of OSL it's usually pretty quick)