For everyone else's reference, I got an Umlindi and the Tenba 10 insert does fit inside.
Its almost a perfect fit, depending on what you have in the rest of the bag it can snag a little bit on the corners when you pull it out.
For reference, the Tenba 10 is 10.5" x 8" x 4.5". For those pictures I've got a Canon 60D with a Sigma 15-50 and a Canon AE-1 with a 50mm prime with a decent amount of extra room for film\sd cards\batteries\filters
Before buying the Tenba I did some searching and couldn't find much about camera inserts and the Umlindi so hopefully this post helps someone out in the future. I also have the FStop Medium Slope ICU and even the shallow side was a little too big to fit in the Umlindi.