I have an Arc Blast, and the first few hikes I took it on involved a bear can carry. I have the Bear Vault 500, which is 8.7" in diameter, by 12.7 inches tall. It carried ok, I didn't really notice it much. Initially, it did press into the space behind the net arc, I could feel it against my back, but it wasn't terrible. there was enough space to pack my rain-gear around it.
The height is the biggest issue, I think. It has to ride above the cross bar, and there weren't a high number of rolls on the top. The Bearikade Week-ender should work ok, it is shorter than the Bear Vault 500, but I don't know about the Expedition. Somewhere there is a thread about Custom Bearikades, and the 12 inch height being the most popular. Might hit the sweet spot between the 2 sizes, and give you the capacity you need for a thru-hike, without being too tall for the bag.
The pack I had before the Blast was a SMD Traveler panel loader. I carried the bear canister inside the pack. I much prefer the Arc Blast for the carry, it doesn't dig into my back like the carry with the Traveler did. I do rather miss the panel loading feature, but the suspension on the Traveler would bug me each time I wore it until I got used to it again.
One little caution: My pack was the original design, 52 L size. I did send it back for the modifications of the 2nd cross bar and the different design of the mesh back. I'm pretty sure I had a bear can carry after the mods with the second cross-bar, but I can't remember for sure.