REI Flash 45 and a Bear Can

Take the pack into REI and try it out with the bear cans there.

Or make a cardboard mockup of your desired bear can (hopefully you haven't yet recycled all your Christmas cardboard), using the specs on the manufacturers' websites, and try that in the pack.

My 40 liter pack holds a Bearikade Weekender sideways, just barely. However, mine is a Six Moon Designs pack that was discontinued in early 2006, so that won't help you much.

They only had the HUGE Garcia there, which basically fills the entire main compartment. I happened to be in the area for work today, otherwise it's about an hour trip for me. I wish I had thought of mocking up different sizes!

I was exactly where you were at last summer: tempted by the good deal on the Flash 45 but struggling with the bear can issue. Truthfully, once I realized there was a) no good way of fitting my Bearikade Weekender in it without making things a pain in the backside elsewhere and 2) the Flash did not save a lot of weight over my Exos 58 (35 oz without the floating top pouch), I gave up the whole idea. A smaller canister would probably make it worthwhile–it seems like a solid pack.

I have a Flash 45 and a couple of different bear cans.

If you didn't like how the pack felt with a Garcia can you won't like it any better with a Weekender as those two cans have almost identical dimensions.

The little Bare Boxer Contender will fit just fine though.

For a weekend trip where you food fits in the smallest bear can the Flash 45 really is perfect. However if you need food for a week in a full size bear can you will need a larger pack.