Lighten Your Load / Trash compactor bag vs. Rain cover

First, apologies for my long pause of #100daysofwilderness. I went on a trip to the Bay Area and then spent the last week processing a decision not to go on a reality TV show. It was kind of emotional! Excuses excuses...really I just lost motivation this past week, but I'm back now! 

Okay, so I'm all about shaving ounces and tenths of ounces off my pack weight, so let me share why I'm a 99% trash compactor bag lady convert (that doesn't roll off the tongue very easily). This information is great for beginners so you don't waste money on a rain cover when you can use a trash bag!

Below is my REI rain cover (4.2oz) versus my trash compactor bag (2.3oz). That's a 1.9oz difference!

First, definitions.
Rain cover - A cover that goes over your backpack to protect it and the contents inside, from rain (or other moist elements).
Trash compactor bag (TCB)- A plastic bag that tends to be thicker and more durable than a traditional trash bag, hence less chances of leaks/rips/tears.

If you dig around on ultralight/lightweight sites, you'll notice many people recommending trash compactor bags instead of buying a rain cover. Have you noticed that yet? Well, when I first saw that suggestion, I was like..."Eh, I don't want to get the outside of my pack to get wet....everything's going to be messy in my pack....I don't believe in wasting plastic bags....etc." Really, what I thought was that it just looked cooler and more official to have a logo-ed rain cover. I admit, it was a bit naive of me to think but hey, it was what it was!

Why I'm 99% converted
Trash compactor bags are awesome because of the durability, weight, and effectiveness. It's compact and slides in nicely into your pack and does it's job. After you insert it, just roll it up on top and everything inside it will stay dry, granted you don't open it wide open in the rain. There are things about a rain cover that I'll miss, like the fact that it covers my entire pack, not just the core of it, or how I can access the bottom of my pack with the zipper. (But why would I need to access my sleeping bag during a rainy hike anyway?)

Why I'm hesitating that 1%
With the way my pack is designed, the TCB only protects the stuff in the main compartment of my pack. What about the contents of my brain (that's the top large pocket that usually flaps over, not my literal brain)? You can mitigate that issue by carrying an ultralight umbrella, keeping brain contents inside a large freezer ziploc bag, or getting a backpack that only has a one main compartment. 

SQS-trashbag.jpg

Would you try this? Why or why not?