I just use an £18 tapered 13l Airlok and it is rock solid.

Tent poles add a bit more rigidity I suppose, but they’re not needed.

The key is to get a strap joining each side of the closed opening around the seatpost. similar pic on the product page on Alpkit’s website.

tapered 13l Airlok

thats exactly what I have just bought

closed opening

what is that…?

He means the roll-top closure at the opposite end to the tapered bit. Instead of clipping the two parts of that buckle together you clip one of the straps in there and wrap that around the seat post and cinch it up. Look at the second image from the “More images” bit here: https://www.alpkit.com/products/airlok-xtra-tapered

oh yes I did that – still felt wobbly and needed 4 hands to strap it all together.
Maybe not too bad while riding?

It’s all the same thing if you ask me. And it’s really just a case of deciding what you want to take on a particular trip and then deciding how you are going to carry it all. (top tip, what ever you do, it’s not on your back, I think we’ve all been there! 😆 )

oh yes I did that – still felt wobbly and needed 4 hands to strap it all together.
Maybe not too bad while riding?

I did the same , and with two webbing straps and a bunji cord it was just about acceptable to ride with but a disaster to get into in a hurry……

without the bunji it was waggling its tail like a dog…..

Here’s a better pic, I add a shoelace 😀 to take the tension off the closure buckles. That strap, round the seatpost, and the other around the bag and saddle rails. Velcro loop bag’s nose to seatpost too.

Once mounted, you have to pull the strap ends to cinch it up tight, pushing on the bag as you do it.

My partner and I use the lightweight setup. We’ve gone on overnight trips and longer journeys of up to 3 weeks. I’ve got lots of tips, trips and gear reviews over on my blog including pack lists so you can see how much can be carried. Faraway Visions

@farawayvisions – Thanks, Meraid – love the blog! That’s a really useful resource. 🙂