Hi, Bee
I own a Gregory Advent Pro, and it's a fantastic lightweight pack. I use it for 3-5 day backpack trips, but I travel light. Fully loaded, with food, fuel, & water is still less than 35 lb.
Excellent suspension systen, & the back panel breathes well.

The silicon-impregnated fabric is pretty thin, but the bottom is rugged Nylon, and the mesh side panels protect the middle half. The upper portion sits well protected behind your head & shoulders, but it's definitely not as durable as the pack cloth used in the MEC Fiamma.

I've hiked alot in Gaspasie, Cartier, Saguenay, and the low growing spruce in your area is brutal on equipment when you have to bushwhack off-trail. Just have to be a bit careful pushing thru the thick stuff, but the pack sits in place well. I'm still amazed at it's water repellant finish,as well.

For on trail use, the Advent Pro is great, but in your area for off-trail SAR work, I'd go with the Fiamma (excellent value) or look at the Gregory G-Pack.

It's almost identical to the Advent Pro, 200 inches more storage, but uses a thicker siliconized material. The Advent also has bottom & back acess, the G-Pack is a top-Loader only.
I assume the G30 fabric in the Advent is 1.3 oz. cloth and the G-pack G70 is using 1.7oz. cloth. Both Gregory packs will have more usable space than the Fiamma, due to the layout and great exterior mesh pockets on the back, sides, and on the hipbelt.
I see the Fiamma comes in red also. That's better in black fly season, they are drawn to the darker colors. Unfortunately, the G-Pack is available in dark Green only.

G-pack:
http://www.gregorypacks.com/prod.php?ID=15

CA Dealers are listed here:
http://www.gregorypacks.com/canada.html

Good luck, and hello and thanks to all the other Forum members whose advice I've read here.