Would it be possible to post a photo showing the modified inserts? I too have this bag (as well as the 107 and 207).
That's why I said additional inserts and a pair of scissors!
Basically, take two 8x15 superflex inserts, cut the small parts off, giving you two squares of 8x8 and 15 high. Put beside each other in the bag (instead of one 8x15x15 supaflex insert with an 8x8 and about 8x4 spaces). The bag comfortably accommodates more than the manufaturer's spec of 15 wide.
I have got 6 supaflex inserts, one 7x15, three 8x15 and two 8x18. I have cut the short parts of each giving me six squares, one 7x7, three 8x8 and to high 8x8. Organised in three rows of two. leaves me with enough space at one end for my 5D with say 24-105 zoom.