Speaking from my personal experience testing the Crumpler 5, 6 and 7MDH here. For your setup, you will need a 7MDH or above. I can confirm right now, as other online reviews have shown, that the length of the 70-200 vertically rested is just nice the height of the 6MDH's internals. So if you MUST have your 50D attached to a 70-200 in the bag, you'll need either the 7 or 8MDH. I personally went for the 6MDH after testing all equipment to snug fit because even though I would've appreciated the extra space in the 7MDH for an extra RM50, I found that even the 6MDH is already a wee bit large to be lugging around as my walkaround bag. Plus the fact that it's a sling bag, so weight can be a real issue to your shoulders. As for the comparison between the 7MDH and 8MDH, there is a larger difference in size compared to 6MDH vs. 7MDH. But for your setup, the 8MDH would be pretty excessive, and the difference in pricing is also more significant compared to the 6MDH vs. 7MDH. I myself have configured my 6MDH to fit a 500D + grip + kitlens facing down, 55-250, 50mm, 580EX II, Raynox, 2 chargers and a rocket blower, with slots remaining for small booklets and the mesh area for extra memory cards + batteries.